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+
+
+Lymphatic vessel
+
+Fig. 3.9  Right breast.
+
+Lactiferous sinuses
+
+Lactiferous ducts
+Mammary glands
+
+Deep (pectoral) fascia
+
+133
+Thorax
+
+
+
+KEY FEATURES Vertebral level TIV/V
+When  working  with  patients,  physicians  use  vertebral levels to determine the position of important anatomical structures within body regions.
+The  horizontal  plane  passing  through  the  disc  that separates thoracic vertebrae TIV and TV is one of the most significant planes in the body (Fig. 3.10) because it:
+
+
+Venous shunts from left to right
+The right atrium is the chamber of the heart that receives deoxygenated blood returning from the body. It lies on the right side of  the midline, and the two major veins, the superior and inferior venae cavae, that drain into it are also located on the right side of the body. This means that, to get to the right side of the body, all blood coming from the left side has to cross the midline. This left-to-right
+
+
+■     passes through the sternal angle anteriorly, marking the position of  the anterior articulation of  the costal cartilage of rib II with the sternum. The sternal angle is used to find the position of rib II as a reference for counting ribs (because of the overlying clavicle, rib I is not palpable);
+■     separates the superior mediastinum from the inferior mediastinum and marks the position of  the superior limit of the pericardium;
+■     marks where the arch of the aorta begins and ends;
+■     passes through the site where the superior vena cava penetrates the pericardium to enter the heart;
+■     is the level at which the trachea bifurcates into right and left main bronchi; and
+■     marks the superior limit of the pulmonary trunk.
+
+shunting is carried out by a number of important and, in some cases, very large veins, several of which are in the thorax (Fig. 3.11).
+In  adults,  the  left  brachiocephalic  vein  crosses  the midline  immediately  posterior  to  the  manubrium  and delivers blood from the left side of the head and neck, the left upper limb, and part of the left thoracic wall into the superior vena cava.
+The hemiazygos and accessory hemiazygos veins drain posterior and lateral parts of  the left thoracic wall, pass immediately anterior to the bodies of thoracic vertebrae, and flow into the azygos vein on the right side, which ultimately connects with the superior vena cava.
+
+
+
+
+
+
+
+Superior mediastinum
+
+Aortic arch
+
+Sternal angle
+
+Trachea
+
+
+Rib II
+
+TIV
+
+
+
+
+
+TV
+
+
+
+
+
+
+
+
+Inferior mediastinum
+
+
+
+
+134	Fig. 3.10  Vertebral level TIV/V.
+Conceptual Overview  •  Key Features	3
+
+
+
+
+
+
+
+
+
+
+
+
+
+Left internal jugular vein
+
+
+
+
+
+
+Superior vena cava
+
+
+Right atrium
+
+Left brachiocephalic vein
+Intercostal vein
+
+Accessory hemiazygos vein
+
+
+
+Azygos vein
+
+
+
+
+
+Hemiazygos vein
+
+
+
+
+Inferior vena cava
+
+
+
+
+
+
+
+
+
+
+Fig. 3.11  Left-to-right venous shunts.
+
+
+
+
+
+
+
+
+
+
+135
+Thorax
+
+
+
+
+Segmental neurovascular supply of thoracic wall
+
+The arrangement of  vessels and nerves that supply the thoracic wall reflects the segmental organization of  the
+
+■     a pair of vessels, the internal thoracic arteries, which run along the deep aspect of the anterior thoracic wall on either side of the sternum.
+
+Posterior and anterior intercostal vessels branch seg-
+
+wall. Arteries to the wall arise from two sources:                       mentally from these arteries and pass laterally around the wall, mainly along the inferior margin of  each rib
+
+■     the thoracic aorta, which is in the posterior mediasti-num, and
+
+
+(Fig. 3.12A). Running with these vessels are intercostal nerves (the anterior rami of thoracic spinal nerves), which innervate the wall, related parietal pleura, and associated
+
+
+
+
+
+
+Left common carotid artery Right subclavian artery
+
+
+
+
+Internal thoracic arteries
+
+Arch of aorta
+
+
+
+Lateral cutaneous branch
+
+Posterior intercostal artery
+
+
+Anterior intercostal artery
+
+
+
+Anterior cutaneous branch
+
+Intercostal nerve
+
+
+
+
+
+
+
+
+
+
+
+A
+
+
+136	Fig. 3.12  A. Segmental neurovascular supply of thoracic wall.
+Conceptual Overview  •  Key Features	3
+
+
+
+
+
+
+T2 T3
+T4 T5
+T2	T6 T7 T8
+T1	T9
+T10 T11
+T12
+
+Supraclavicular nerves
+
+
+
+
+Xiphoid process
+
+Costal margin
+
+Umbilicus
+
+Anterior superior iliac spine
+
+
+
+T2
+
+T3
+T4 T5 T6 T7
+T8 T9
+T10 T11
+T12
+
+
+Inguinal ligament
+
+
+
+
+Pubic tubercles
+
+
+B	C
+
+Fig. 3.12, cont’d  B. Anterior view of thoracic dermatomes associated with thoracic spinal nerves. C. Lateral view of dermatomes associated with thoracic spinal nerves.
+
+
+
+
+
+
+skin. The position of these nerves and vessels relative to the	The   anterosuperior   region   of   the   trunk   receives
+
+ribs must be considered when passing objects, such as chest tubes, through the thoracic wall.
+
+branches from the anterior ramus of C4 via supraclavicu-lar branches of the cervical plexus.
+
+Dermatomes of the thorax generally reflect the segmen-	The  highest  thoracic  dermatome  on  the  anterior
+
+tal organization of the thoracic spinal nerves (Fig. 3.12B). The exception occurs, anteriorly and superiorly, with the first thoracic dermatome, which is located mostly in the upper limb, and not on the trunk.
+
+chest wall is T2, which also extends into the upper limb. In the midline, skin over the xiphoid process is innervated by T6.
+Dermatomes of T7 to T12 follow the contour of the ribs onto the anterior abdominal wall (Fig. 3.12C).
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+137
+Thorax
+
+
+
+
+Sympathetic system
+All preganglionic nerve fibers of the sympathetic system are carried out of the spinal cord in spinal nerves T1 to L2 (Fig.  3.13). This  means  that  sympathetic  fibers  found anywhere in the body ultimately emerge from the spinal cord as components of these spinal nerves. Preganglionic sympathetic fibers destined for the head are carried out of the spinal cord in spinal nerve T1.
+
+
+
+
+
+
+
+
+Paravertebral sympathetic trunk
+
+Flexible wall and inferior thoracic aperture
+The thoracic wall is expandable because most ribs articu-late with other components of the wall by true joints that allow movement, and because of the shape and orientation of the ribs (Fig. 3.14).
+A rib’s posterior attachment is superior to its anterior attachment. Therefore, when a rib is elevated, it moves the anterior thoracic wall forward relative to the posterior wall, which is fixed. In addition, the middle part of each rib is inferior to its two ends, so that when this region of the rib is elevated, it expands the thoracic wall laterally. Finally, because the diaphragm is muscular, it changes the volume of the thorax in the vertical direction.
+Changes in the anterior, lateral, and vertical dimensions of the thoracic cavity are important for breathing.
+
+
+T1
+
+Spinal cord
+
+
+Spinal nerve	Elevation of lateral aspect of ribs in inspiration
+
+
+Sternum moves forward in inspiration because of rib elevation
+
+
+
+
+L2
+
+
+
+
+
+
+
+
+
+
+
+
+Gray ramus communicans
+
+
+Spinal cord
+
+Spinal nerve
+
+
+
+
+
+
+
+Thoracic sympathetic ganglion
+
+Sympathetic trunk
+
+
+
+White ramus communicans
+
+
+
+Diaphragm descends to increase thoracic capacity in inspiration
+
+
+138	Fig. 3.13  Sympathetic trunks.	Fig. 3.14  Flexible thoracic wall and inferior thoracic aperture.
+Conceptual Overview  •  Key Features	3
+
+
+
+
+Innervation of the diaphragm
+The diaphragm is innervated by two phrenic nerves that originate, one on each side, as branches of  the cervical plexus in the neck (Fig. 3.15). They arise from the anterior rami of  cervical nerves C3, C4, and C5, with the major contribution coming from C4.
+The phrenic nerves pass vertically through the neck, the  superior  thoracic  aperture,  and  the  mediastinum to  supply  motor  innervation  to  the  entire  diaphragm, including the crura (muscular extensions that attach the
+
+diaphragm to the upper lumbar vertebrae). In the media-stinum, the phrenic nerves pass anteriorly to the roots of the lungs.
+The tissues that initially give rise to the diaphragm are in an anterior position on the embryological disc before the head fold develops, which explains the cervical origin of the nerves that innervate the diaphragm. In other words, the tissue that gives rise to the diaphragm originates supe-rior to the ultimate location of the diaphragm.
+Spinal cord injuries below the level of the origin of the phrenic nerve do not affect movement of the diaphragm.
+
+
+
+
+
+
+C3
+
+C4
+C5
+
+
+Right phrenic nerve	Left phrenic nerve
+
+
+
+Pericardial branch of phrenic nerve
+
+
+
+
+
+
+
+Pericardium
+
+
+
+
+
+Diaphragm
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 3.15  Innervation of the diaphragm.	139
+Thorax
+
+
+Regional anatomy
+
+The cylindrical thorax consists of:	Carcinoma of the breast creates tension on these ligaments,
+
+
+■     a wall,
+■     two pleural cavities, ■     the lungs, and
+■     the mediastinum.
+
+The thorax houses the heart and lungs, acts as a conduit
+
+causing pitting of the skin.
+In nonlactating women, the predominant component of the breasts is fat, while glandular tissue is more abun-dant in lactating women.
+The breast lies on deep fascia related to the pectoralis major muscle and other surrounding muscles. A layer of loose connective tissue (the retromammary space) sepa-
+
+
+
+for structures passing between the neck and the abdomen, and plays a principal role in breathing. In addition, the thoracic wall protects the heart and lungs and provides support  for  the  upper  limbs.  Muscles  anchored  to  the anterior thoracic wall provide some of this support, and together with their associated connective tissues, nerves, and vessels, and the overlying skin and superficial fascia, define the pectoral region.
+
+rates the breast from the deep fascia and provides some degree of movement over underlying structures.
+The base, or attached surface, of each breast extends vertically from ribs II to VI, and transversely from the sternum to as far laterally as the midaxillary line.
+
+Arterial supply
+The breast is related to the thoracic wall and to structures associated with the upper limb; therefore, vascular supply and drainage can occur by multiple routes (Fig. 3.16):
+
+
+
+PECTORAL REGION
+
+The pectoral region is external to the anterior thoracic wall and helps anchor the upper limb to the trunk. It consists of:
+
+
+■     laterally,  vessels  from  the  axillary  artery—superior thoracic, thoraco-acromial, lateral thoracic, and sub-scapular arteries;
+■     medially, branches from the internal thoracic artery;
+
+
+
+■     a superficial compartment containing skin, superficial fascia, and breasts; and
+■     a deep compartment containing muscles and associated
+
+■     the second to fourth intercostal arteries via branches that perforate the thoracic wall and overlying muscle.
+
+
+
+structures.
+
+Nerves, vessels, and lymphatics in the superficial com-partment emerge from the thoracic wall, the axilla, and the neck.
+
+
+Breast
+The breasts consist of  mammary glands and associated skin  and  connective  tissues.  The  mammary  glands are modified sweat glands in the superficial fascia anterior to the pectoral muscles and the anterior thoracic wall (Fig. 3.16).
+The mammary glands consist of a series of ducts and
+
+
+Venous drainage
+Veins draining the breast parallel the arteries and ulti-mately  drain  into  the  axillary,  internal  thoracic,  and intercostal veins.
+
+Innervation
+Innervation of the breast is via anterior and lateral cutane-ous branches of the second to sixth intercostal nerves. The nipple is innervated by the fourth intercostal nerve.
+
+Lymphatic drainage
+Lymphatic drainage of the breast is as follows:
+
+
+
+associated secretory lobules. These converge to form 15 to 20 lactiferous ducts, which open independently onto the nipple. The nipple is surrounded by a circular pigmented area of skin termed the areola.
+A well-developed, connective tissue stroma surrounds the ducts and lobules of the mammary gland. In certain regions, this condenses to form well-defined ligaments, the suspensory ligaments of breast, which are continuous
+140	with  the  dermis  of  the  skin  and  support  the  breast.
+
+■     Approximately 75% is via lymphatic vessels that drain laterally and superiorly into axillary nodes (Fig. 3.16).
+■     Most  of  the  remaining  drainage  is  into  parasternal nodes deep to the anterior thoracic wall and associated with the internal thoracic artery.
+■     Some drainage may occur via lymphatic vessels that follow the lateral branches of posterior intercostal arter-ies and connect with intercostal nodes situated near the heads and necks of ribs.
+Regional Anatomy  •  Pectoral Region	3
+
+
+
+Internal thoracic artery
+
+Pectoral branch of
+thoracoacromial artery	Pectoralis major muscle
+
+Apical axillary nodes
+
+
+Central axillary nodes
+
+
+
+Lateral thoracic artery
+
+
+Lateral axillary nodes
+
+
+Pectoral axillary nodes
+
+
+
+Axillary process
+
+
+
+Lymphatic and venous drainage passes from lateral and superior part of the breast into axilla
+
+
+
+Areola
+
+
+
+Secretory lobules
+
+Secretory lobules
+
+Suspensory ligaments
+
+Lactiferous ducts
+
+
+
+Lactiferous sinuses
+
+
+Retromammary space
+
+
+
+Parasternal nodes
+
+
+
+
+Mammary branches of internal thoracic artery
+
+Lymphatic and venous
+drainage passes from medial part of the breast parasternally
+
+Some lymphatic and venous drainage may pass from inferior part of the breast into the abdomen
+
+
+
+Fig. 3.16  Breasts.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+141
+Thorax
+
+
+
+Axillary nodes drain into the subclavian trunks, para-sternal nodes drain into the bronchomediastinal trunks, and intercostal nodes drain either into the thoracic duct or into the bronchomediastinal trunks.
+
+
+Breast in men
+The breast in men is rudimentary and consists only of small ducts, often composed of cords of cells, that normally do not extend beyond the areola. Breast cancer can occur in men.
+
+
+
+
+
+
+
+In the clinic
+
+Axillary tail of breast
+It is important for clinicians to remember when evaluating the breast for pathology that the upper lateral region of the breast can project around the lateral margin of the pectoralis major muscle and into the axilla. This axillary process (axillary tail) may perforate deep fascia and extend as far superiorly as the apex of the axilla.
+
+
+
+
+
+
+
+
+
+
+In the clinic
+
+Breast cancer
+Breast cancer is one of the most common malignancies in women. It develops in the cells of the acini, lactiferous ducts, and lobules of the breast. Tumor growth and spread depends on the exact cellular site of origin of the cancer. These factors affect the response to surgery, chemotherapy, and radiotherapy. Breast tumors spread via the lymphatics and veins, or by direct invasion.
+When a patient has a lump in the breast, a diagnosis of breast cancer is confirmed by a biopsy and histological evaluation. Once confirmed, the clinician must attempt to stage the tumor.
+Staging the tumor means defining the:
+
+■     size of the primary tumor,
+■     exact site of the primary tumor,
+■     number and sites of lymph node spread, and ■     organs to which the tumor may have spread.
+
+Computed tomography (CT) scanning of the body may be carried out to look for any spread to the lungs (pulmonary metastases), liver (hepatic metastases), or bone (bony metastases).
+Further imaging may include bone scanning using
+142	radioactive isotopes, which are avidly taken up by the tumor
+
+
+
+metastases in bone, and PET-CT, which can visualize active foci of the metastatic disease in the body.
+Lymph drainage of the breast is complex. Lymph vessels pass to axillary, supraclavicular, and parasternal nodes and may even pass to abdominal lymph nodes, as well as to the opposite breast. Containment of nodal metastatic breast cancer is therefore potentially difficult because it can spread through many lymph node groups.
+Subcutaneous lymphatic obstruction and tumor growth pull on connective tissue ligaments in the breast, resulting in the appearance of an orange peel texture (peau d’orange) on the surface of the breast. Further subcutaneous spread can induce a rare manifestation of breast cancer that produces a hard, woody texture to the skin (cancer en cuirasse).
+A mastectomy (surgical removal of the breast) involves excision of breast tissue. Within the axilla the breast tissue must be removed from the medial axillary wall. Closely applied to the medial axillary wall is the long thoracic nerve. Damage to this nerve can result in paralysis of the serratus anterior muscle, producing a characteristic “winged” scapula. It is also possible to damage the nerve to the latissimus dorsi muscle, and this may affect extension, medial rotation, and adduction of the humerus.
+Regional Anatomy  •  Pectoral Region	3
+
+
+
+Muscles of the pectoral region
+Each pectoral region contains the pectoralis major, pecto-ralis minor, and subclavius muscles (Fig. 3.17 and Table 3.1). All originate from the anterior thoracic wall and insert into bones of the upper limb.
+
+
+
+
+
+Pectoralis major
+
+
+Pectoralis major
+The pectoralis  major muscle is the largest and most superficial of the pectoral region muscles. It directly under-lies the breast and is separated from it by deep fascia and the loose connective tissue of the retromammary space.
+
+
+
+Subclavius
+Lateral pectoral nerve
+
+Thoraco-acromial artery
+
+
+
+
+
+
+
+Pectoralis minor Medial pectoral nerve Lateral thoracic artery
+
+Clavipectoral fascia
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 3.17  Muscles and fascia of the pectoral region.
+
+
+
+
+
+Table 3.1
+
+Muscle
+
+Muscles of the pectoral region
+
+Origin	Insertion	Innervation	Function
+
+
+
+Pectoralis major
+
+
+
+
+Subclavius
+
+
+Pectoralis minor
+
+Medial half of clavicle and anterior surface of sternum, first seven costal cartilages, aponeurosis of external oblique
+Rib I at junction between rib and costal cartilage
+
+Anterior surfaces of the third, fourth, and fifth ribs, and deep fascia overlying the related intercostal spaces
+
+Lateral lip of intertubercular sulcus of humerus
+
+
+
+Groove on inferior surface of middle third of clavicle
+
+Coracoid process of scapula
+
+Medial and lateral pectoral nerves
+
+
+
+Nerve to subclavius
+
+
+Medial pectoral nerves
+
+Adduction, medial rotation, and flexion of the humerus at the shoulder joint
+
+
+Pulls clavicle medially to stabilize sternoclavicular joint; depresses tip of shoulder
+Depresses tip of shoulder; protracts scapula
+
+143
+Thorax
+
+
+
+The pectoralis major has a broad origin that includes the anterior surfaces of the medial half of the clavicle, the sternum, and related costal cartilages. The muscle fibers converge to form a flat tendon, which inserts into the
+
+
+THORACIC WALL
+
+The thoracic wall is segmental in design and composed of skeletal elements and muscles. It extends between:
+
+
+
+lateral lip of the intertubercular sulcus of the humerus. The  pectoralis  major  adducts,  flexes,  and  medially
+rotates the arm.
+
+Subclavius and pectoralis minor muscles
+The subclavius and pectoralis minor muscles underlie
+
+
+■     the superior thoracic aperture, bordered by vertebra TI, rib I, and the manubrium of the sternum; and
+■     the  inferior  thoracic  aperture,  bordered  by  vertebra TXII, rib XII, the end of rib XI, the costal margin, and the xiphoid process of the sternum.
+
+the pectoralis major:	Skeletal framework
+
+■     The subclavius is small and passes laterally from the anterior and medial part of rib I to the inferior surface of the clavicle.
+■     The pectoralis minor passes from the anterior surfaces of ribs III to V to the coracoid process of the scapula.
+
+Both the subclavius and pectoralis minor pull the tip of
+
+
+The  skeletal  elements  of  the  thoracic  wall  consist  of the  thoracic  vertebrae,  intervertebral  discs,  ribs,  and sternum.
+
+Thoracic vertebrae
+There are twelve thoracic vertebrae, each of which is characterized by articulations with ribs.
+
+
+
+the shoulder inferiorly.
+A continuous layer of deep fascia, the clavipectoral fascia, encloses the subclavius and pectoralis minor and attaches to the clavicle above and to the floor of the axilla below.
+The muscles of  the pectoral region form the anterior wall of the axilla, a region between the upper limb and the neck through which all major structures pass. Nerves, vessels, and lymphatics that pass between the pectoral region and the axilla pass through the clavipectoral fascia between the subclavius and pectoralis minor or pass under the inferior margins of the pectoralis major and minor.
+
+
+Anterior
+
+
+Typical thoracic vertebra
+A typical thoracic vertebra has a heart-shaped vertebral body, with roughly equal dimensions in the transverse and anteroposterior directions, and a long spinous process (Fig. 3.18). The vertebral foramen is generally circular and the laminae are broad and overlap with those of the vertebra below. The superior articular processes are flat, with their articular surfaces facing almost directly posteriorly, while the inferior articular processes project from the laminae and their articular facets face anteriorly.
+
+
+Superior articular process
+
+
+
+
+Facet for articulation Vertebral body	with tubercle of rib
+
+
+Superior
+
+
+Superior demifacet
+
+
+
+Vertebral foramen
+
+
+
+
+
+Spinous process
+
+Facet for articulation with tubercle of rib
+
+
+Pedicle
+
+
+
+
+Lamina
+
+Transverse process
+
+Posterior
+
+
+Posterior
+
+
+
+
+
+
+Inferior articular process
+
+
+Anterior
+
+
+
+
+Inferior
+
+Demifacets for articulation with head of ribs
+
+
+Superior view	Superolateral view
+
+144	Fig. 3.18  Typical thoracic vertebra.
+Regional Anatomy  •  Thoracic Wall	3
+
+
+The transverse processes are club shaped and project posterolaterally.
+
+Articulation with ribs
+A typical thoracic vertebra has three sites on each side for	Vertebra TI articulation with ribs.
+
+■     Two demifacets (i.e., partial facets) are located on the superior and inferior aspects of the body for articulation with corresponding sites on the heads of adjacent ribs. The superior costal facet articulates with part of the head of  its own rib, and the inferior costal facet
+articulates with part of the head of the rib below.	Superior costal facet for head of rib I ■     An oval facet (transverse costal facet) at the end of
+the transverse process articulates with the tubercle of its own rib.
+
+Not all vertebrae articulate with ribs in the same fashion
+(Fig. 3.19):	Vertebra TX
+
+■     The superior costal facets on the body of vertebra TI are complete and articulate with a single facet on the head of its own rib—in other words, the head of rib I does not articulate with vertebra CVII.
+■     Similarly, vertebra TX (and often TIX) articulates only with its own ribs and therefore lacks inferior demifacets on the body.
+■     Vertebrae TXI and TXII articulate only with the heads
+of their own ribs—they lack transverse costal facets and	Single complete costal facet for head of rib X have only a single complete facet on each side of their
+bodies.
+
+
+Ribs
+There are twelve pairs of ribs, each terminating anteriorly	Vertebra TXI in a costal cartilage (Fig. 3.20).
+Although all ribs articulate with the vertebral column, only the costal cartilages of the upper seven ribs, known as true ribs, articulate directly with the sternum. The remaining five pairs of ribs are false ribs:
+
+
+■     The costal cartilages of ribs VIII to X articulate anteri-orly with the costal cartilages of the ribs above.
+■     Ribs  XI  and  XII  have  no  anterior  connection  with other ribs or with the sternum and are often called floating ribs.
+
+
+
+
+No costal facet on transverse process
+
+Fig. 3.19  Atypical thoracic vertebrae.
+
+
+A typical rib consists of a curved shaft with anterior and posterior ends (Fig. 3.21). The anterior end is continuous with its costal cartilage. The posterior end articulates with the vertebral column and is characterized by a head, neck,
+and tubercle.	145
+Thorax
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+True ribs I–VII	Intercostal space
+
+Costal cartilage
+
+
+Posterior	Tubercle
+Angle
+Head
+
+
+
+
+Neck
+Internal surface
+
+Costal groove
+
+Costal cartilage
+
+
+
+
+
+
+Anterior A
+
+External surface
+
+
+Tubercle	Neck
+
+
+Crest
+
+
+
+False ribs VIII–XII	Floating ribs
+
+Costal margin
+
+
+Nonarticular surface
+
+B
+
+
+Articular facets
+Articular facet
+
+
+Fig. 3.20  Ribs.
+Fig. 3.21  A typical rib. A. Anterior view. B. Posterior view of proximal end of rib.
+
+
+
+
+
+
+
+
+
+
+
+
+146
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+The head is somewhat expanded and typically presents two articular surfaces separated by a crest. The smaller superior surface articulates with the inferior costal facet on the body of the vertebra above, whereas the larger inferior facet articulates with the superior costal facet of its own vertebra.
+The neck is a short flat region of bone that separates the head from the tubercle.
+The tubercle projects posteriorly from the junction of the neck with the shaft and consists of  two regions, an articular part and a nonarticular part:
+
+
+Rib I
+Head	Neck
+
+
+
+
+
+
+
+
+Scalene tubercle
+
+
+Tubercle
+
+
+
+
+
+
+
+
+
+Grooves
+
+
+■     The articular part is medial and has an oval facet for articulation with a corresponding facet on the trans-verse process of the associated vertebra.
+■     The raised nonarticular part is roughened by ligament attachments.
+
+
+The shaft is generally thin and flat with internal and external surfaces.
+The superior margin is smooth and rounded, whereas the inferior margin is sharp. The shaft bends forward just
+laterally to the tubercle at a site termed the angle. It also	Rib XII has a gentle twist around its longitudinal axis so that the
+external surface of  the anterior part of  the shaft faces somewhat superiorly relative to the posterior part. The inferior margin of  the internal surface is marked by a
+
+
+Costal cartilage
+
+
+
+distinct costal groove.
+
+Distinct features of upper and lower ribs
+The upper and lower ribs have distinct features (Fig. 3.22).
+
+Rib I
+Rib I is flat in the horizontal plane and has broad superior and inferior surfaces. From its articulation with vertebra TI, it slopes inferiorly to its attachment to the manubrium of the sternum. The head articulates only with the body of vertebra TI and therefore has only one articular surface. Like other ribs, the tubercle has a facet for articulation with the transverse process. The superior surface of the rib is characterized by a distinct tubercle, the scalene tubercle, which separates two smooth grooves that cross the rib approximately midway along the shaft. The anterior groove is caused by the subclavian vein, and the posterior groove is caused by the subclavian artery. Anterior and posterior
+
+
+Fig. 3.22  Atypical ribs.
+
+
+to these grooves, the shaft is roughened by muscle and liga-ment attachments.
+
+Rib II
+Rib II, like rib I, is flat but twice as long. It articulates with the vertebral column in a way typical of most ribs.
+
+Rib X
+The head of rib X has a single facet for articulation with its own vertebra.
+
+Ribs XI and XII
+Ribs XI and XII articulate only with the bodies of their own vertebrae and have no tubercles or necks. Both ribs are short, have little curve, and are pointed anteriorly.
+
+
+
+
+
+
+
+147
+Thorax
+
+
+
+
+Sternum
+
+upper  half  of  the  anterior  end  of  the  second  costal cartilage.
+
+
+
+The adult sternum consists of three major elements: the broad  and  superiorly  positioned  manubrium  of   the sternum, the narrow and longitudinally oriented body of the  sternum,  and  the  small  and  inferiorly  positioned xiphoid process (Fig. 3.23).
+
+Manubrium of the sternum
+The manubrium of the sternum forms part of the bony framework of the neck and the thorax.
+The superior surface of  the manubrium is expanded laterally  and  bears  a  distinct  and  palpable  notch,  the jugular notch (suprasternal notch), in the midline. On either side of this notch is a large oval fossa for articula-tion with the clavicle. Immediately inferior to this fossa, on each lateral surface of the manubrium, is a facet for the attachment of the first costal cartilage. At the lower end of the lateral border is a demifacet for articulation with the
+
+
+
+
+Articular site for clavicle
+
+
+
+Attachment site for rib I
+
+
+Body of the sternum
+The body of the sternum is flat.
+The anterior surface of the body of the sternum is often marked by transverse ridges that represent lines of fusion between the segmental elements called sternebrae, from which this part of the sternum arises embryologically.
+The lateral margins of the body of the sternum have articular facets for costal cartilages. Superiorly, each lateral margin has a demifacet for articulation with the inferior aspect of the second costal cartilage. Inferior to this demi-facet are four facets for articulation with the costal carti-lages of ribs III to VI.
+At the inferior end of  the body of  the sternum is a demifacet for articulation with the upper demifacet on the seventh costal cartilage. The inferior end of the body of the sternum is attached to the xiphoid process.
+
+
+
+
+Jugular notch
+
+Manubrium of sternum
+
+
+Sternal angle (manubriosternal joint)
+
+
+Articular demifacets for rib II
+
+
+
+Transverse ridges
+
+
+
+
+Articular facets for ribs III–VI
+
+
+
+
+
+
+Articular facets for rib VII
+
+
+Body of sternum
+
+
+
+
+
+
+Xiphoid process
+
+
+148	Fig. 3.23  Sternum.
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+
+Xiphoid process
+The xiphoid process is the smallest part of the sternum. Its shape is variable: it may be wide, thin, pointed, bifid, curved, or perforated. It begins as a cartilaginous structure, which becomes ossified in the adult. On each side of  its upper lateral margin is a demifacet for articulation with the inferior end of the seventh costal cartilage.
+
+
+Joints
+Costovertebral joints
+A typical rib articulates with:
+
+Together, the costovertebral joints and related ligaments allow the necks of the ribs either to rotate around their longitudinal axes, which occurs mainly in the upper ribs, or to ascend and descend relative to the vertebral column, which  occurs  mainly  in  the  lower  ribs. The  combined movements of all of the ribs on the vertebral column are essential for altering the volume of  the thoracic cavity during breathing.
+
+Joint with head of rib
+The two facets on the head of the rib articulate with the superior facet on the body of its own vertebra and with the inferior facet on the body of the vertebra above. This joint is divided into two synovial compartments by an intra-
+
+
+
+■     the bodies of adjacent vertebrae, forming a joint with the head of the rib; and
+■     the transverse process of its related vertebra, forming a costotransverse joint (Fig. 3.24).
+
+articular ligament, which attaches the crest to the adjacent intervertebral disc and separates the two articular surfaces on the head of the rib. The two synovial compartments and the intervening ligament are surrounded by a single joint
+
+
+
+
+
+
+
+
+Vertebra
+
+Joint capsule
+
+
+Superior costotransverse ligament
+
+
+Rib
+
+
+
+
+
+Joint cavities
+
+
+
+
+
+
+
+
+
+Costotransverse ligament
+
+
+Disc
+
+Intra-articular ligament
+
+Vertebra
+
+
+
+
+
+
+Lateral costotransverse
+Joint with vertebral body	ligament
+
+
+Costotransverse joint
+
+Superolateral view	Superior view
+
+Fig. 3.24  Costovertebral joints.
+
+
+
+149
+Thorax
+
+
+
+capsule attached to the outer margins of  the combined articular surfaces of the head and vertebral column.
+
+Costotransverse joints
+
+■     The lateral costotransverse ligamentis lateral to the joint and attaches the tip of the transverse process to the roughened nonarticular part of the tubercle of the rib.
+
+Costotransverse  joints  are  synovial  joints  between	A third ligament, the superior costotransverse liga-
+
+the tubercle of  a rib and the transverse process of  the related  vertebra  (Fig.  3.24).  The  capsule  surrounding each joint is thin. The joint is stabilized by two strong extracapsular ligaments that span the space between the transverse process and the rib on the medial and lateral sides of the joint:
+
+ment, attaches the superior surface of the neck of the rib to the transverse process of the vertebra above.
+Slight gliding movements occur at the costotransverse joints.
+
+Sternocostal joints
+The sternocostal joints are joints between the upper seven
+
+
+
+■     The costotransverse ligament is medial to the joint and  attaches  the  neck  of  the  rib  to  the  transverse process.
+
+costal cartilages and the sternum (Fig. 3.25).
+The  joint  between  rib  I  and  the  manubrium  is  not synovial and consists of  a fibrocartilaginous connection
+
+
+
+
+
+Manubriosternal joint (symphysis)
+
+Fibrocartilaginous joint
+
+
+
+
+Sternal angle
+
+Synovial joint
+(two compartments)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Synovial joint
+
+
+
+
+Xiphisternal joint (symphysis)
+
+
+
+
+
+
+Interchondral joints
+
+
+150	Fig. 3.25  Sternocostal joints.
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+between  the  manubrium  and  the  costal  cartilage. The second to seventh joints are synovial and have thin cap-sules reinforced by surrounding sternocostal ligaments.
+The joint between the second costal cartilage and the sternum is divided into two compartments by an intra-articular  ligament.  This  ligament  attaches  the  second costal cartilage to the junction of the manubrium and the body of the sternum.
+
+Interchondral joints
+Interchondral joints occur between the costal cartilages of adjacent ribs (Fig. 3.25), mainly between the costal carti-lages of ribs VII to X, but may also involve the costal carti-lages of ribs V and VI.
+Interchondral joints provide indirect anchorage to the sternum and contribute to the formation of a smooth infe-rior costal margin. They are usually synovial, and the thin fibrous capsules are reinforced by interchondral ligaments.
+
+Manubriosternal and xiphisternal joints
+The joints between the manubrium and the body of the sternum and between the body of  the sternum and the xiphoid process are usually symphyses (Fig. 3.25). Only slight angular movements occur between the manubrium and the body of the sternum during respiration. The joint between the body of the sternum and the xiphoid process often becomes ossified with age.
+A clinically useful feature of the manubriosternal joint is that it can be palpated easily. This is because the manu-brium  normally  angles  posteriorly  on  the  body  of  the sternum, forming a raised feature referred to as the sternal angle. This elevation marks the site of articulation of rib II with the sternum. Rib I is not palpable, because it lies inferior to the clavicle and is embedded in tissues at the base of the neck. Therefore, rib II is used as a reference for counting ribs and can be felt immediately lateral to the sternal angle.
+In addition, the sternal angle lies on a horizontal plane that passes through the intervertebral disc between verte-brae TIV and TV (see Fig. 3.10). This plane separates the superior mediastinum from the inferior mediastinum and marks the superior border of the pericardium. The plane also passes through the end of the ascending aorta and the beginning of the arch of the aorta, the end of the arch of the aorta and the beginning of the thoracic aorta, and the bifurcation of the trachea, and just superior to the pulmo-nary trunk (see Fig. 3.79 and 3.86).
+
+
+Intercostal spaces
+Intercostal spaces lie between adjacent ribs and are filled by intercostal muscles (Fig. 3.26).
+
+Intercostal nerves and associated major arteries and veins lie in the costal groove along the inferior margin of the superior rib and pass in the plane between the inner two layers of muscles.
+In each space, the vein is the most superior structure and is therefore highest in the costal groove. The artery is inferior to the vein, and the nerve is inferior to the artery and often not protected by the groove. Therefore, the  nerve  is  the  structure  most  at  risk  when  objects perforate  the  upper  aspect  of   an  intercostal  space. Small collateral branches of the major intercostal nerves and  vessels  are  often  present  superior  to  the  inferior rib below.
+Deep to the intercostal spaces and ribs, and separating these structures from the underlying pleura, is a layer of loose  connective  tissue,  called  endothoracic  fascia, which contains variable amounts of fat.
+Superficial  to  the  spaces  are  deep  fascia,  superficial fascia, and skin. Muscles associated with the upper limbs and back overlie the spaces.
+
+
+
+
+
+
+In the clinic
+
+Cervical ribs
+Cervical ribs are present in approximately 1% of the population.
+A cervical rib is an accessory rib articulating with vertebra CVII; the anterior end attaches to the superior border of the anterior aspect of rib I.
+Plain radiographs may demonstrate cervical ribs as small horn-like structures (see Fig. 3.106).
+It is often not appreciated by clinicians that a fibrous band commonly extends from the anterior tip of the small cervical ribs to rib I, producing a “cervical band” that is not visualized on radiography. In patients with cervical ribs and cervical bands, structures that normally pass over rib I (see Fig. 3.7) are elevated by, and pass over, the cervical rib and band.
+Clinically, “thoracic outlet syndrome” is used to describe symptoms resulting from abnormal compression of the brachial plexus of nerves as it passes over the first rib and through the axillary inlet into the upper limb. The anterior ramus of T1 passes superiorly out of the superior thoracic aperture to join and become part of the brachial plexus. The cervical band from a cervical rib is one cause of thoracic outlet syndrome by
+putting upward stresses on the lower parts of the brachial plexus as they pass over the cervical band and related
+cervical rib.	151
+Thorax
+
+
+
+Posterior ramus of spinal nerve	Posterior intercostal artery and vein
+
+
+
+
+
+
+
+
+
+
+
+Lateral branches of intercostal nerve and vessels
+
+
+Intercostal nerve	Aorta
+
+
+Costal groove
+
+
+
+Internal thoracic artery and vein
+
+Anterior cutaneous branch of intercostal nerve
+
+
+
+Collateral branches of intercostal nerve and vessels
+
+
+
+
+Anterior intercostal artery and vein
+
+Anterior perforating branches of intercostal vessels
+
+
+A
+
+
+
+
+Serratus anterior muscle
+
+
+
+External intercostal muscle
+
+Internal intercostal muscle
+
+Innermost intercostal muscle
+
+
+Skin
+
+Superficial fascia
+
+Lung
+
+Pleural cavity
+Visceral pleura
+Parietal pleura
+
+
+Intercostal vein
+
+Intercostal artery
+
+Intercostal nerve
+
+Collateral branches
+
+
+
+B	Endothoracic fascia
+
+Fig. 3.26  Intercostal space. A. Anterolateral view. B. Details of an intercostal space and relationships.
+
+
+
+
+
+
+
+152
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+Internal thoracic artery
+
+Anterior cutaneous branch
+
+
+External intercostal muscle
+
+
+Anterior perforating branch
+
+Anterior intercostal artery
+
+
+Internal intercostal muscle
+
+
+Innermost intercostal muscle
+
+Lateral cutaneous branch
+
+Mediastinum
+
+
+
+Right Lung	Left Lung
+
+
+
+Lateral cutaneous branch
+
+
+
+Aorta
+
+
+
+
+Anterior ramus	Posterior intercostal artery (intercostal nerve)
+C	Posterior ramus	Spinal nerve
+
+Fig. 3.26, cont’d  Intercostal space. C. Transverse section.
+
+
+
+In the clinic
+
+Collection of sternal bone marrow
+The subcutaneous position of the sternum makes it possible to place a needle through the hard outer cortex into the internal (or medullary) cavity containing bone marrow. Once the needle is in this position, bone marrow can be aspirated. Evaluation of this material under the microscope helps clinicians diagnose certain blood diseases such as leukemia.
+
+
+
+In the clinic
+
+Rib fractures
+Single rib fractures are of little consequence, though extremely painful.
+After severe trauma, ribs may be broken in two or more places. If enough ribs are broken, a loose segment of chest wall, a flail segment (flail chest), is produced. When the patient takes a deep inspiration, the flail segment moves in the opposite direction to the chest wall, preventing full lung expansion and creating a paradoxically moving segment. If a large enough segment of chest wall is affected, ventilation may be impaired and assisted ventilation may be required until the ribs have healed.
+
+Muscles
+Muscles of  the thoracic wall include those that fill and support the intercostal spaces, those that pass between the sternum and the ribs, and those that cross several ribs between costal attachments (Table 3.2).
+The  muscles  of   the  thoracic  wall,  together  with muscles between the vertebrae and ribs posteriorly (i.e., the levatores costarum and serratus posterior supe-rior  and  serratus  posterior  inferior  muscles)  alter the position of  the ribs and sternum and so change the thoracic volume during breathing. They also reinforce the thoracic wall.
+
+
+Intercostal muscles
+
+The intercostal muscles are three flat muscles found in each intercostal space that pass between adjacent ribs (Fig. 3.27). Individual muscles in this group are named according to their positions:
+
+■     The   external   intercostal   muscles   are   the   most superficial.
+■     The   internal   intercostal   muscles   are   sandwiched between the external and innermost muscles.
+■     The innermost intercostal muscles are the deepest of the
+three muscles.	153
+Thorax
+
+
+
+Table 3.2
+
+Muscle
+
+Muscles of the thoracic wall
+
+Superior attachment	Inferior attachment	Innervation	Function
+
+
+
+External intercostal
+
+
+
+Internal intercostal
+
+
+
+Innermost intercostal
+
+Subcostales
+
+Transversus thoracis
+
+Inferior margin of rib above
+
+
+
+Lateral edge of costal groove of rib above
+
+
+Medial edge of costal groove of rib above
+Internal surface (near angle) of lower ribs
+Inferior margins and internal surfaces of costal cartilages of second to sixth ribs
+
+Superior margin of rib below
+
+
+
+Superior margin of rib below deep to the attachment of the related external intercostal
+
+Internal aspect of superior margin of rib below
+Internal surface of second or third rib below
+Inferior aspect of deep surface of body of sternum, xiphoid process, and costal cartilages of ribs IV–VII
+
+Intercostal nerves; T1–T11
+
+
+Intercostal nerves; T1–T11
+
+
+Intercostal nerves; T1–T11
+Related intercostal nerves
+Related intercostal nerves
+
+Most active during inspiration; supports intercostal space; moves ribs superiorly
+Most active during expiration; supports intercostal space; moves ribs inferiorly
+Acts with internal intercostal muscles
+May depress ribs
+
+Depresses costal cartilages
+
+
+
+
+
+
+External intercostal muscle  Intercostal nerve
+Intercostal artery Intercostal vein
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Internal intercostal muscle
+
+Innermost intercostal muscle
+
+Collateral branches
+
+
+
+External intercostal membrane
+
+External intercostal muscle
+
+
+
+
+
+
+Fig. 3.27  Intercostal muscles.
+
+
+
+154
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+The intercostal muscles are innervated by the related intercostal nerves. As a group, the intercostal muscles provide structural support for the intercostal spaces during breathing. They can also move the ribs.
+
+External intercostal muscles
+The eleven pairs of external intercostal muscles extend from the inferior margins (lateral edges of costal grooves) of the ribs above to the superior margins of the ribs below. When the thoracic wall is viewed from a lateral position, the muscle fibers pass obliquely anteroinferiorly (Fig. 3.27). The muscles extend around the thoracic wall from the regions of the tubercles of the ribs to the costal cartilages, where each layer continues as a thin connective tissue aponeurosis  termed  the  external  intercostal  mem-brane. The external intercostal muscles are most active in inspiration.
+
+Internal intercostal muscles
+The eleven pairs of internal intercostal muscles pass between the most inferior lateral edge of the costal grooves of the ribs above, to the superior margins of the ribs below. They extend from parasternal regions, where the muscles course between adjacent costal cartilages, to the angle of the ribs posteriorly (Fig. 3.27). This layer continues medi-ally toward the vertebral column, in each intercostal space, as  the  internal  intercostal  membrane. The  muscle fibers pass in the opposite direction to those of the external intercostal muscles. When the thoracic wall is viewed from a lateral position, the muscle fibers pass obliquely postero-inferiorly. The internal intercostal muscles are most active during expiration.
+
+Innermost intercostal muscles
+The innermost intercostal muscles are the least distinct of the intercostal muscles, and the fibers have the same orientation as the internal intercostals (Fig. 3.27). These muscles are most evident in the lateral thoracic wall. They extend between the inner surfaces of adjacent ribs from the
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Subcostal muscles
+
+A
+
+
+
+medial edge of the costal groove to the deep surface of the
+rib below. Importantly, the neurovascular bundles associ-	B ated with the intercostal spaces pass around the thoracic
+
+
+Transversus thoracis muscle
+
+
+
+wall in the costal grooves in a plane between the innermost and internal intercostal muscles.
+
+Subcostales
+The subcostales are in the same plane as the innermost intercostals, span multiple ribs, and are more numerous in lower regions of the posterior thoracic wall (Fig. 3.28A). They extend from the internal surfaces of one rib to the internal surface of  the second (next) or third rib below. Their fibers parallel the course of the internal intercostal
+
+
+Fig. 3.28  A. Subcostal muscles. B. Transversus thoracis muscles.
+
+
+muscles and extend from the angle of  the ribs to more medial positions on the ribs below.
+
+Transversus thoracis muscles
+The transversus thoracis muscles are found on the deep surface of the anterior thoracic wall (Fig. 3.28B) and
+in the same plane as the innermost intercostals.	155
+Thorax
+
+
+
+The transversus thoracis muscles originate from the posterior aspect of the xiphoid process, the inferior part of the body of the sternum, and the adjacent costal cartilages of the lower true ribs. They pass superiorly and laterally to insert into the lower borders of the costal cartilages of ribs III  to  VI.  They  most  likely  pull  these  latter  elements inferiorly.
+The transversus thoracis muscles lie deep to the internal thoracic vessels and secure these vessels to the wall.
+
+Arterial supply
+Vessels that supply the thoracic wall consist mainly of posterior  and  anterior  intercostal  arteries,  which  pass around the wall between adjacent ribs in intercostal spaces
+
+(Fig. 3.29). These arteries originate from the aorta and internal thoracic arteries, which in turn arise from the subclavian arteries in the root of the neck. Together, the intercostal arteries form a basket-like pattern of vascular supply around the thoracic wall.
+
+Posterior intercostal arteries
+Posterior  intercostal  arteries  originate  from  vessels associated with the posterior thoracic wall. The upper two posterior intercostal arteries on each side are derived from the supreme intercostal artery, which descends into the thorax as a branch of the costocervical trunk in the neck. The costocervical trunk is a posterior branch of the subclavian artery (Fig. 3.29).
+
+
+
+Supreme intercostal artery
+
+Costocervical trunk
+
+Subclavian artery
+
+
+
+
+Aorta
+
+Posterior intercostal artery
+
+Internal thoracic artery
+
+
+Collateral branch of posterior intercostal artery
+Anterior perforating branches
+
+
+
+
+
+Anterior intercostal artery
+
+
+
+
+
+
+Musculophrenic artery	Superior epigastric artery
+
+
+
+
+
+
+
+
+156	Fig. 3.29  Arteries of the thoracic wall.
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+The remaining nine pairs of posterior intercostal arter-ies arise from the posterior surface of the thoracic aorta. Because the aorta is on the left side of the vertebral column, those  posterior  intercostal  vessels  passing  to  the  right
+
+internal thoracic artery, whereas those supplying the lower spaces arise from the musculophrenic artery.
+In each intercostal space, the anterior intercostal arter-ies usually have two branches:
+
+
+
+side of the thoracic wall cross the midline anterior to the bodies of the vertebrae and therefore are longer than the corresponding vessels on the left.
+In addition to having numerous branches that supply various components of the wall, the posterior intercostal arteries have branches that accompany lateral cutaneous branches of the intercostal nerves to superficial regions.
+
+
+■     One passes below the margin of the upper rib.
+■     The other passes above the margin of the lower rib and meets a collateral branch of  the posterior intercostal artery.
+
+The distributions of the anterior and posterior intercos-
+
+
+
+
+Anterior intercostal arteries
+The anterior intercostal arteries originate directly or indirectly as lateral branches from the internal thoracic arteries (Fig. 3.29).
+Each  internal  thoracic  artery  arises  as  a  major branch of  the subclavian artery in the neck. It passes anteriorly over the cervical dome of the pleura and descends vertically  through  the  superior  thoracic  aperture  and along the deep aspect of  the anterior thoracic wall. On each side, the internal thoracic artery lies posterior to the costal cartilages of the upper six ribs and about 1 cm lateral to the sternum. At approximately the level of  the sixth intercostal space, it divides into two terminal branches:
+
+tal vessels overlap and can develop anastomotic connec-tions. The anterior intercostal arteries are generally smaller than the posterior vessels.
+In addition to anterior intercostal arteries and a number of other branches, the internal thoracic arteries give rise to perforating branches that pass directly forward between the costal cartilages to supply structures external to the thoracic wall. These vessels travel with the anterior cutane-ous branches of the intercostal nerves.
+
+Venous drainage
+Venous drainage from the thoracic wall generally parallels the pattern of arterial supply (Fig. 3.30).
+Centrally,  the  intercostal  veins  ultimately  drain  into
+
+
+
+
+■     the  superior  epigastric  artery,  which  continues inferiorly into the anterior abdominal wall (Fig. 3.29); and
+■     the musculophrenic artery, which passes along the costal margin, goes through the diaphragm, and ends near the last intercostal space.
+
+Anterior intercostal arteries that supply the upper six
+
+the azygos system of  veins or into internal  thoracic veins, which connect with the brachiocephalic veins in the neck.
+Often  the  upper  posterior  intercostal  veins  on  the left  side  come  together  and  form  the  left  superior intercostal vein, which empties into the left brachioce-phalic vein.
+Similarly, the upper posterior intercostal veins on the right side may come together and form the right superior
+
+intercostal  spaces  arise  as  lateral  branches  from  the	intercostal vein, which empties into the azygos vein.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+157
+Thorax
+
+
+
+
+
+
+
+
+
+
+
+
+
+Left superior intercostal vein
+
+
+
+Right brachiocephalic vein
+
+
+
+Right superior intercostal vein
+
+Left brachiocephalic vein
+
+
+
+Accessory hemiazygos vein
+
+
+Posterior intercostal vein
+
+
+Azygos vein	Internal thoracic vein
+
+Anterior perforating branches
+
+
+
+
+
+Anterior intercostal vein
+
+Hemiazygos vein
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 3.30  Veins of the thoracic wall.
+
+
+
+
+
+
+
+
+
+158
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+
+Lymphatic drainage
+Lymphatic vessels of the thoracic wall drain mainly into lymph nodes associated with the internal thoracic arteries (parasternal nodes), with the heads and necks of ribs (intercostal nodes), and with the diaphragm (diaphrag-matic nodes) (Fig. 3.31). Diaphragmatic nodes are poste-rior to the xiphoid and at sites where the phrenic nerves penetrate the diaphragm. They also occur in regions where the diaphragm is attached to the vertebral column.
+Parasternal  nodes  drain  into  bronchomediastinal trunks. Intercostal nodes in the upper thorax also drain into bronchomediastinal trunks, whereas intercostal nodes in the lower thorax drain into the thoracic duct.
+
+Nodes  associated  with  the  diaphragm  interconnect with   parasternal,   prevertebral,   and   juxta-esophageal nodes, brachiocephalic nodes (anterior to the brachio-cephalic veins in the superior mediastinum), and lateral aortic/lumbar nodes (in the abdomen).
+Superficial regions of  the thoracic wall drain mainly into axillary lymph nodes in the axilla or parasternal nodes.
+
+
+Innervation Intercostal nerves
+Innervation of the thoracic wall is mainly by the intercos-tal nerves, which are the anterior rami of spinal nerves
+
+
+
+
+
+Right jugular trunk
+
+Right subclavian trunk
+
+
+Right bronchomediastinal trunk
+
+Brachiocephalic nodes
+
+Thoracic duct
+Left jugular trunk
+
+Left subclavian trunk
+
+Left bronchomediastinal trunk
+
+Left parasternal lymphatic vessel
+
+
+
+Right parasternal lymphatic vessel
+
+Parasternal nodes
+
+Intercostal nodes
+
+
+
+Thoracic duct
+
+
+
+
+Diaphragmatic nodes
+
+
+
+
+
+Diaphragm
+
+Lateral aortic nodes	Cisterna chyli
+
+
+
+
+
+
+Fig. 3.31  Major lymphatic vessels and nodes of the thoracic wall.	159
+Thorax
+
+
+
+T1 to T11 and lie in the intercostal spaces between adjacent ribs. The anterior ramus of spinal nerve T12 (the subcos-tal nerve) is inferior to rib XII (Fig. 3.32).
+A  typical  intercostal  nerve  passes  laterally  around
+
+In addition to these major branches, small collateral branches can be found in the intercostal space running along the superior border of the lower rib.
+In the thorax, the intercostal nerves carry:
+
+
+
+the thoracic wall in an intercostal space. The largest of the branches is the lateral cutaneous branch, which pierces the lateral thoracic wall and divides into an ante-rior branch and a posterior branch that innervate the overlying skin.
+The  intercostal  nerves  end  as  anterior  cutaneous branches, which emerge either parasternally, between adjacent costal cartilages, or laterally to the midline, on the anterior abdominal wall, to supply the skin.
+
+
+■     somatic motor innervation to the muscles of the tho-racic wall (intercostal, subcostal, and transversus tho-racis muscles),
+■     somatic sensory innervation from the skin and parietal pleura, and
+■     postganglionic sympathetic fibers to the periphery.
+
+
+
+
+
+
+
+
+
+
+Posterior ramus	Spinal cord
+
+
+
+
+
+Posterior branch
+
+Lateral cutaneous
+branch	Intercostal nerve
+
+
+Anterior branch
+
+Anterior cutaneous branch
+
+
+Medial branch Small collateral branch
+
+
+Lateral branch
+
+
+Fig. 3.32  Intercostal nerves.
+
+
+
+
+
+
+
+160
+Regional Anatomy  •  Thoracic Wall	3
+
+
+
+Sensory innervation of  the skin overlying the upper thoracic wall is supplied by cutaneous branches (supracla-vicular nerves), which descend from the cervical plexus in the neck.
+In addition to innervating the thoracic wall, intercostal nerves innervate other regions:
+
+■     The lateral cutaneous branch of the second intercostal nerve (the intercostobrachial nerve) contributes to cutaneous innervation of  the medial surface of  the upper arm.
+■     The lower intercostal nerves supply the muscles, skin, and peritoneum of the abdominal wall.
+
+
+■     The anterior ramus of T1 contributes to the brachial plexus.
+
+
+
+
+
+In the clinic
+
+Surgical access to the chest
+A surgical access is potentially more challenging in the chest given the rigid nature of the thoracic cage. Moreover, access is also dependent upon the organ that is operated upon and its relationships to subdiaphragmatic structures and structures in the neck.
+The most common approaches are a median sternotomy and a lateral thoracotomy.
+A median sternotomy involves making a vertical incision in the sternum from just below the sternal notch to the distal end of the xiphoid process. Care must be taken not to cause injury to the vessels, in particular to the brachiocephalic veins. Bleeding from the branches of the internal thoracic artery can occur and needs to be controlled. Opening the sternum causes traction on the upper ribs and may lead to rib fractures. Sometimes partial sternotomy is performed
+
+
+
+
+
+
+
+Air in soft tissues postthoracotomy
+
+Intrathoracic drain
+
+Right lung
+
+Neo-esophagus
+
+
+
+with the incision involving only the upper part of the sternum and ending at the level of manubriosternal junction or just below. A median sternotomy allows access to the heart, including coronary arteries and valves, pericardium, great vessels, anterior mediastinum, and thymus, as well as to the lower trachea. It can also be used for removal of retrosternal goiter or during esophagectomy. The incision can be extended laterally into the supraclavicular region, giving access to the subclavian and carotid arteries.
+A lateral thoracotomy gives access to the ipsilateral hemithorax and its contents including the lung, mediastinum, esophagus, and heart (left lateral thoracotomy) (Fig. 3.33).
+However, it involves division of muscles of the thoracic wall which leads to significant postoperative pain that needs to be well controlled to avoid restricted lung function. The
+
+
+
+
+
+
+
+
+Ascending aorta Pulmonary artery
+
+Left lung
+
+Descending thoracic aorta
+
+
+
+
+
+
+
+Fig. 3.33  Right thoracotomy for esophageal cancer with intrathoracic large-bore drain. In this case, a neo-esophagus has been fashioned from the stomach.
+
+(continues)	161
+Thorax
+
+
+
+In the clinic—cont’d
+
+incision starts at the anterior axillary line and then passes below the tip of the scapula and is extended superiorly between the posterior midline and medial border of the scapula. The pleural cavity is entered through an intercostal space. In older patients and those with osteoporosis, a short segment of rib is often resected to minimize the risk of a rib fracture.
+
+
+
+
+
+
+
+In the clinic
+
+Thoracostomy (chest) tube insertion
+Insertion of a chest tube is a commonly performed procedure and is indicated to relieve air or fluid trapped in the thorax between the lung and the chest wall (pleural cavity). This procedure is done for pneumothorax, hemothorax, hemopneumothorax, malignant pleural effusion empyema, hydrothorax, and chylothorax, and also after thoracic surgery.
+The position of the thoracostomy tube is usually between the anterior axillary and midaxillary anatomical lines from anterior to posterior and in either the fourth or fifth intercostal space. The position of the ribs in this region should be clearly marked. Anesthetic should be applied to the superior border of the rib and the inferior aspect of the intercostal space, including one rib and space above and one rib and space below. The neurovascular bundle runs in the neurovascular plane, which lies in the superior aspect of the intercostal space (just below the rib); hence, the reason for positioning the tube on the superior border of a rib (i.e., at the lowest position in the intercostal space).
+Chest tube insertion is now commonly done with direct ultrasound guidance. This approach allows the physician both to assess whether the pleural effusion is simple or complex and loculated, and to select the safest site for entering the pleural space. In some cases of pneumothorax, a chest drain can be inserted under computed tomography-guidance, especially in patients with underlying lung disease where it is difficult to differentiate a large bulla from free air in the pleural space.
+
+
+
+Minimally invasive thoracic surgery (video-assisted thoracic surgery [VATS]) involves making small (1-cm) incisions in the intercostal spaces, placing a small camera on a telescope, and manipulating other instruments through additional small incisions. A number of procedures can be performed in this manner, including lobectomy, lung biopsy, and esophagectomy.
+
+
+
+
+
+
+
+In the clinic
+
+Intercostal nerve block
+Local anesthesia of intercostal nerves produces excellent analgesia in patients with chest trauma and in those patients requiring anesthesia for a thoracotomy, mastectomy, or upper abdominal surgical procedures.
+The intercostal nerves are situated inferior to the rib borders in the neurovascular bundle. Each neurovascular bundle is situated deep to the external and internal intercostal muscle groups.
+The nerve block may be undertaken using a “blind” technique or under direct imaging guidance.
+The patient is placed in the appropriate position to access the rib. Typically, under ultrasound guidance, a needle may be advanced into the region of the subcostal groove, followed by an injection with a local anesthetic. Depending on the type of anesthetic used, analgesia may be short- or long-acting.
+Given the position of the neurovascular bundle and the subcostal groove, complications may include puncture of the parietal pleura and an ensuing pneumothorax. Bleeding may also occur if the artery or vein is damaged during the procedure.
+
+
+
+
+
+
+
+
+162
+Regional Anatomy  •  Diaphragm	3
+
+
+
+
+DIAPHRAGM
+
+The  diaphragm  is  a  thin  musculotendinous  structure that fills the inferior thoracic aperture and separates the thoracic cavity from the abdominal cavity (Fig. 3.34 and see Chapter 4). It is attached peripherally to the:
+
+From these peripheral attachments, muscle fibers con-verge  to  join  the  central  tendon.  The  pericardium  is attached to the middle part of the central tendon.
+In  the  median  sagittal  plane,  the  diaphragm  slopes inferiorly  from  its  anterior  attachment  to  the  xiphoid, approximately at vertebral level TVIII/IX, to its posterior attachment to the median arcuate ligament, crossing
+
+
+
+
+■     xiphoid process of the sternum,
+■     costal margin of the thoracic wall, ■     ends of ribs XI and XII,
+■     ligaments that span across structures of the posterior abdominal wall, and
+
+anteriorly to the aorta at approximately vertebral level TXII.
+Structures traveling between the thorax and abdomen pass through the diaphragm or between the diaphragm and its peripheral attachments:
+
+■     vertebrae of the lumbar region.	■     The  inferior  vena  cava  passes  through  the  central tendon at approximately vertebral level TVIII.
+
+
+
+
+
+
+
+
+
+
+
+Right phrenic nerve
+
+Right pericardiacophrenic artery
+
+Right vagus nerve
+
+Esophagus
+
+Left phrenic nerve
+
+Left pericardiacophrenic artery
+
+Left vagus nerve
+
+Internal thoracic arteries
+
+Esophageal hiatus
+
+
+Inferior vena cava
+
+Central tendon of diaphragm
+Aortic hiatus Phrenic nerves
+
+Inferior phrenic arteries
+
+
+Superior epigastric artery
+
+
+
+Musculophrenic artery
+
+Right crus
+
+
+Abdominal aorta
+
+
+
+
+
+Fig. 3.34  Diaphragm.	163
+Thorax
+
+
+■     The esophagus passes through the muscular part of the           Contraction of  the domes of  the diaphragm flattens diaphragm, just to the left of midline, approximately at       the   diaphragm,   thereby   increasing   thoracic   volume.
+
+vertebral level TX.
+■     The vagus nerves pass through the diaphragm with the esophagus.
+■     The aorta passes behind the posterior attachment of the diaphragm at vertebral level TXII.
+■     The thoracic duct passes behind the diaphragm with the aorta.
+■     The  azygos  and  hemiazygos  veins  may  also  pass through the aortic hiatus or through the crura of the diaphragm.
+
+Other structures outside the posterior attachments of
+
+Movements of  the diaphragm are essential for normal breathing.
+
+MOVEMENTS OF THE THORACIC WALL AND DIAPHRAGM DURING BREATHING
+
+One of the principal functions of the thoracic wall and the diaphragm is to alter the volume of the thorax and thereby move air in and out of the lungs.
+During breathing, the dimensions of the thorax change in  the  vertical,  lateral,  and  anteroposterior  directions. Elevation and depression of  the diaphragm significantly
+
+the diaphragm lateral to the aortic hiatus include the sympathetic trunks. The greater, lesser, and least splanch-nic nerves penetrate the crura.
+
+Arterial supply
+The arterial supply to the diaphragm is from vessels that arise superiorly and inferiorly to it (see Fig. 3.34). From above, pericardiacophrenic and musculophrenic arteries supply the diaphragm. These vessels are branches of the internal thoracic arteries. Superior phrenic arteries, which  arise  directly  from  lower  parts  of  the  thoracic aorta, and small branches from intercostal arteries con-tribute to the supply. The largest arteries supplying the diaphragm  arise  from  below  it. These  arteries  are  the inferior phrenic arteries, which branch directly from the abdominal aorta.
+
+Venous drainage
+Venous drainage of the diaphragm is by veins that gener-ally parallel the arteries. The veins drain into:
+
+alter the vertical dimensions of  the thorax. Depression results when the muscle fibers of the diaphragm contract. Elevation occurs when the diaphragm relaxes.
+Changes in the anteroposterior and lateral dimensions result from elevation and depression of the ribs (Fig. 3.35). The posterior ends of the ribs articulate with the vertebral column, whereas the anterior ends of most ribs articulate with the sternum or adjacent ribs.
+Because the anterior ends of the ribs are inferior to the posterior ends, when the ribs are elevated, they move the sternum upward and forward. Also, the angle between the body of the sternum and the manubrium may become slightly less acute. When the ribs are depressed, the sternum moves  downward  and  backward. This  “pump  handle” movement changes the dimensions of  the thorax in the anteroposterior direction (Fig. 3.35A).
+As well as the anterior ends of the ribs being lower than the posterior ends, the middles of  the shafts tend to be lower than the two ends. When the shafts are elevated, the middles of the shafts move laterally. This “bucket handle”
+
+
+■     the brachiocephalic veins in the neck, ■     the azygos system of veins, or
+■     abdominal veins (left suprarenal vein and inferior vena cava).
+
+movement increases the lateral dimensions of the thorax (Fig. 3.35B).
+Any muscles attaching to the ribs can potentially move one rib relative to another and therefore act as accessory respiratory muscles. Muscles in the neck and the abdomen
+
+Innervation	can fix or alter the positions of upper and lower ribs.
+The diaphragm is innervated by the phrenic nerves (C3, C4, and C5), which penetrate the diaphragm and innervate it from its abdominal surface.
+
+
+
+
+
+
+
+164
+Regional Anatomy  •  Movements of the Thoracic Wall and Diaphragm During Breathing	3
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Superior and anterior movement of sternum
+
+
+
+
+
+
+A
+
+
+
+
+
+
+Pump handle
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Bucket handle movement
+
+In the clinic
+
+Diaphragmatic paralysis
+In cases of phrenic nerve palsy, diaphragmatic paralysis ensues, which is manifested by the elevation of the diaphragm muscle on the affected side (Fig. 3.36). The most important cause of the phrenic nerve palsy that should never be overlooked is malignant infiltration of the nerve by lung cancer. Other causes include postviral neuropathy (in particular, related to varicella zoster virus), trauma, iatrogenic injury during thoracic surgery, and degenerative changes in the cervical spine with compression of the C3–C5 nerve roots.
+Most patients with unilateral diaphragmatic paralysis are asymptomatic and require no treatment. Some may report shortness of breath, particularly on exertion. Bilateral paralysis of the diaphragm is rare but can cause significant respiratory distress.
+Surgical plication of the diaphragm can be performed in cases with respiratory compromise and is often done laparoscopically. The surgeon creates folds in the paralyzed diaphragm and sutures them in place, reducing the mobility of the diaphragmatic muscle. There is usually good improvement in lung function, exercise tolerance, and shortness of breath after the procedure.
+
+Right lung	Aorta	Left lung
+
+
+
+
+
+
+
+
+
+
+
+
+Elevation of lateral shaft of rib
+
+
+
+B
+
+Elevated right diaphragm	Heart  Left diaphragm
+
+
+
+Fig. 3.35  Movement of thoracic wall during breathing. A. Pump handle movement of ribs and sternum. B. Bucket handle movement of ribs.
+
+Fig. 3.36  Chest radiograph showing an elevated right hemidiaphragm in a patient with right-sided diaphragmatic paralysis.
+
+
+
+
+
+
+
+165
+Thorax
+
+
+
+PLEURAL CAVITIES
+
+Two pleural cavities, one on either side of  the media-stinum, surround the lungs (Fig. 3.37):
+
+■     Pleura that reflects from the medial wall and onto the surface of the lung is visceral pleura (Fig. 3.37), which adheres to and covers the lung.
+
+Each  pleural  cavity  is  the  potential  space  enclosed
+
+
+
+■     Superiorly, they extend above rib I into the root of the neck.
+■     Inferiorly, they extend to a level just above the costal margin.
+
+
+between the visceral and parietal pleurae. They normally contain only a very thin layer of serous fluid. As a result, the surface of the lung, which is covered by visceral pleura, directly opposes and freely slides over the parietal pleura
+
+■     The   medial   wall   of   each   pleural   cavity   is   the	attached to the wall.
+
+mediastinum.
+
+Pleura
+Each pleural cavity is lined by a single layer of flat cells, mesothelium, and an associated layer of supporting con-nective tissue; together, they form the pleura.
+
+
+Parietal pleura
+The  names  given  to  the  parietal  pleura  correspond  to the  parts  of  the  wall  with  which  they  are  associated (Fig. 3.38):
+
+
+
+The pleura is divided into two major types, based on location:
+
+■     Pleura related to the ribs and intercostal spaces is termed the costal part.
+
+
+
+
+■     Pleura associated with the walls of a pleural cavity is parietal pleura (Fig. 3.37).
+
+
+
+
+Parietal pleura
+Visceral pleura
+Pleural cavity
+
+■     Pleura covering the diaphragm is the diaphragmatic part.
+■     Pleura covering the mediastinum is the mediastinal part.
+■     The dome-shaped layer of  parietal pleura lining the cervical  extension  of  the  pleural  cavity  is  cervical pleura (dome of pleura or pleural cupola).
+
+
+Mediastinum	Suprapleural membrane
+
+Rib I	Cervical pleura
+
+
+
+Right	Left lung lung
+
+
+Pleura surrounding structures in root of lung
+
+
+Pulmonary ligament
+Costal part
+Mediastinal part
+
+Rib VIII	Diaphragmatic part
+
+
+
+Rib X
+
+
+
+Diaphragm
+
+
+
+166	Fig. 3.37  Pleural cavities.	Fig. 3.38  Parietal pleura.
+Regional Anatomy  •  Pleural Cavities	3
+
+
+
+Covering the superior surface of the cervical pleura is a distinct dome-like layer of fascia, the suprapleural mem-brane (Fig. 3.38). This connective tissue membrane is attached laterally to the medial margin of the first rib and behind to the transverse process of vertebra CVII. Superi-orly, the membrane receives muscle fibers from some of the deep muscles in the neck (scalene muscles) that function to keep the membrane taut. The suprapleural membrane provides apical support for the pleural cavity in the root of the neck.
+In the region of vertebrae TV to TVII, the mediastinal pleura reflects off the mediastinum as a tubular, sleeve-like covering for structures (i.e., airway, vessels, nerves, lym-phatics) that pass between the lung and mediastinum. This sleeve-like covering and the structures it contains forms the root of  the lung. The root joins the medial surface of  the lung at an area referred to as the hilum of  the lung. Here, the mediastinal pleura is continuous with the visceral pleura.
+The parietal pleural is innervated by somatic afferent fibers. The costal pleura is innervated by branches from the intercostal nerves, and pain would be felt in relation to the thoracic wall. The diaphragmatic pleura and the mediasti-nal pleura are innervated mainly by the phrenic nerves (originating at spinal cord levels C3, C4, and C5). Pain from
+
+
+Midclavicular line
+
+Midaxillary line
+
+
+
+
+
+
+
+
+
+
+
+
+Vertebra TXII (posterior)
+
+Rib X (lateral)	Rib VIII (anterior)
+
+
+
+
+
+
+Fig. 3.39  Pleural reflections.
+
+these areas would refer to the C3, C4, and C5 dermatomes       the inferior margin courses somewhat horizontally, cross-(lateral  neck  and  the  supraclavicular  region  of   the       ing  ribs  XI  and  XII  to  reach  vertebra TXII.  From  the
+
+shoulder).
+
+
+Peripheral reflections
+
+The  peripheral  reflections  of  parietal  pleura  mark  the extent of the pleural cavities (Fig. 3.39).
+Superiorly, the pleural cavity can project as much as 3 to 4 cm above the first costal cartilage but does not extend above the neck of rib I. This limitation is caused by the inferior slope of  rib I to its articulation with the manubrium.
+Anteriorly,  the  pleural  cavities  approach  each  other posterior  to  the  upper  part  of  the  sternum.  However, posterior to the lower part of  the sternum, the parietal pleura does not come as close to the midline on the left side as it does on the right because the middle media-stinum, containing the pericardium and heart, bulges to the left.
+Inferiorly, the costal pleura reflects onto the diaphragm above the costal margin. In the midclavicular line, the pleural cavity extends inferiorly to approximately rib VIII. In the midaxillary line, it extends to rib X. From this point,
+
+midclavicular line to the vertebral column, the inferior boundary of the pleura can be approximated by a line that runs between rib VIII, rib X, and vertebra TXII.
+
+Visceral pleura
+The visceral pleura is continuous with the parietal pleura at the hilum of each lung, where structures enter and leave the organ. The visceral pleura is firmly attached to the surface of the lung, including both opposed surfaces of the fissures that divide the lungs into lobes.
+Although the visceral pleura is innervated by visceral afferent nerves that accompany bronchial vessels, pain is generally not elicited from this tissue.
+
+Pleural recesses
+The lungs do not completely fill the anterior or posterior inferior regions of  the pleural cavities (Fig. 3.40). This results in recesses in which two layers of parietal pleura become opposed. Expansion of the lungs into these spaces usually occurs only during forced inspiration; the recesses also provide potential spaces in which fluids can collect and from which fluids can be aspirated.
+
+
+
+167
+Thorax
+
+
+
+
+Costomediastinal recesses
+Anteriorly, a costomediastinal recess occurs on each side where costal pleura is opposed to mediastinal pleura. The largest is on the left side in the region overlying the heart (Fig. 3.40).
+
+Costodiaphragmatic recesses
+The largest and clinically most important recesses are the costodiaphragmatic  recesses,  which  occur  in  each pleural cavity between the costal pleura and diaphragmatic pleura (Fig. 3.40). The costodiaphragmatic recesses are the regions between the inferior margin of the lungs and infe-rior margin of the pleural cavities. They are deepest after forced expiration and shallowest after forced inspiration.
+
+
+
+
+
+
+Midclavicular line
+
+
+Midaxillary line
+
+During quiet respiration, the inferior margin of the lung crosses rib VI in the midclavicular line and rib VIII in the midaxillary line, and then courses somewhat horizontally to reach the vertebral column at vertebral level TX. Thus, from the midclavicular line and around the thoracic wall to the vertebral column, the inferior margin of the lung can be approximated by a line running between rib VI, rib VIII, and vertebra TX. The inferior margin of the pleural cavity at the same points is rib VIII, rib X, and vertebra TXII. The costodiaphragmatic recess is the region between the two margins.
+During expiration, the inferior margin of the lung rises and the costodiaphragmatic recess becomes larger.
+
+
+
+
+
+
+
+
+
+Parietal pleura
+
+Visceral pleura
+
+
+
+
+
+
+
+Costodiaphragmatic recess
+
+
+
+
+Vertebra TX	Costomediastinal recess (posterior)
+
+Rib VIII (lateral)
+
+
+Costodiaphragmatic recess
+
+Rib VI (anterior)
+
+
+
+
+
+
+
+
+168	Fig. 3.40  Parietal pleural reflections and recesses.
+Regional Anatomy  •  Pleural Cavities	3
+
+
+
+In the clinic
+
+Pleural effusion
+A pleural effusion occurs when excess fluid accumulates within the pleural space. As the fluid accumulates within the pleural space the underlying lung is compromised and may collapse as the volume of fluid increases. Once a pleural effusion has been diagnosed, fluid often will be aspirated to determine the cause, which can include infection, malignancy, cardiac failure, hepatic disease, and pulmonary embolism. A large pleural effusion needs to be drained to allow the collapsed part of the lung to reexpand and improve breathing (Fig. 3.41).
+
+
+Aorta	Left lung
+
+In the clinic
+
+Pneumothorax
+A pneumothorax is a collection of gas or air within the pleural cavity (Fig. 3.42). When air enters the pleural cavity the tissue elasticity of the parenchyma causes the lung to collapse within the chest, impairing the lung function. Occasionally, the gas within the pleural cavity may accumulate to such an extent that the mediastinum is “pushed” to the opposite side, compromising the other lung. This is termed a tension pneumothorax and requires urgent treatment.
+Most pneumothoraces are spontaneous (i.e., they occur in the absence of no known pathology and no known lung disease). In addition, pneumothoraces may occur as a result of trauma, inflammation, smoking, and other underlying pulmonary diseases. Certain pulmonary metastases, such as in patients with osteosarcoma, may cause spontaneous pneumothorax especially after chemotherapy. The occurrence of pneumothorax interferes with cancer treatment and increases mortality.
+The symptoms of pneumothorax are often determined by the degree of air leak and the rate at which the accumulation of gas occurs and the ensuing lung collapses. They include pain, shortness of breath, and cardiorespiratory collapse, if severe.
+
+
+
+
+
+Right lung	   Left empyema with air-fluid level
+
+Air in subcutaneous tissues
+
+Pneumothorax
+
+Left lung
+
+
+Fig. 3.41  CT image of left pleural effusion.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Right lung	Heart
+
+Fig. 3.42  Pneumothorax in a patient with extensive subcutaneous emphysema.
+
+169
+Thorax
+
+
+
+
+Lungs
+The two lungs are organs of respiration and lie on either side of the mediastinum surrounded by the right and left pleural cavities. Air enters and leaves the lungs via main bronchi, which are branches of the trachea.
+The  pulmonary  arteries  deliver  deoxygenated  blood
+
+It may stabilize the position of the inferior lobe and may also  accommodate  the  down-and-up  translocation  of structures in the root during breathing.
+In the mediastinum, the vagus nerves pass immediately posterior to the roots of the lungs, while the phrenic nerves pass immediately anterior to them.
+Within each root and located in the hilum are:
+
+
+
+to the lungs from the right ventricle of the heart. Oxygen-ated blood returns to the left atrium via the pulmonary veins.
+The right lung is normally a little larger than the left lung  because  the  middle  mediastinum,  containing  the heart, bulges more to the left than to the right.
+Each lung has a half-cone shape, with a base, apex, two surfaces, and three borders (Fig. 3.43).
+
+
+■     a pulmonary artery,
+■     two pulmonary veins, ■     a main bronchus,
+■     bronchial vessels, ■     nerves, and
+■     lymphatics.
+
+
+
+
+■     The base sits on the diaphragm.
+■     The apex projects above rib I and into the root of the neck.
+■     The two surfaces—the costal surface lies immediately adjacent  to  the  ribs  and  intercostal  spaces  of  the thoracic wall. The mediastinal surface lies against the mediastinum anteriorly and the vertebral column posteriorly  and  contains  the  comma-shaped  hilum of   the  lung,  through  which  structures  enter  and leave.
+■     The three borders—the inferior border of the lung is sharp and separates the base from the costal surface. The  anterior  and  posterior  borders  separate  the costal surface from the medial surface. Unlike the ante-
+
+Generally, the pulmonary artery is superior at the hilum, the pulmonary veins are inferior, and the bronchi are somewhat posterior in position.
+On the right side, the lobar bronchus to the superior lobe branches from the main bronchus in the root, unlike on the left where it branches within the lung itself, and is superior to the pulmonary artery.
+
+Right lung
+The right  lung has three lobes and two fissures (Fig. 3.45A). Normally, the lobes are freely movable against each other because they are separated, almost to the hilum, by invaginations of  visceral pleura. These invaginations form the fissures:
+
+
+
+rior and inferior borders, which are sharp, the posterior border is smooth and rounded.
+
+The lungs lie directly adjacent to, and are indented by, structures contained in the overlying area. The heart and major vessels form bulges in the mediastinum that indent the medial surfaces of the lung; the ribs indent the costal
+
+■     The  oblique  fissure  separates  the  inferior  lobe (lower lobe) from the superior lobe and the middle lobe of the right lung.
+■     The horizontal  fissure separates the superior lobe (upper lobe) from the middle lobe.
+
+The approximate position of  the oblique fissure on a
+
+
+
+surfaces. Pathology, such as tumors, or abnormalities in one structure can affect the related structure.
+
+
+Root and hilum
+The root of  each lung is a short tubular collection of structures that together attach the lung to structures in the mediastinum (Fig. 3.44). It is covered by a sleeve of medi-astinal pleura that reflects onto the surface of the lung as visceral pleura. The region outlined by this pleural reflec-tion on the medial surface of the lung is the hilum, where structures enter and leave.
+A thin blade-like fold of pleura projects inferiorly from the root of  the lung and extends from the hilum to the
+170	mediastinum. This structure is the pulmonary ligament.
+
+patient, in quiet respiration, can be marked by a curved line on the thoracic wall that begins roughly at the spinous process of the vertebra TIV level of the spine, crosses the fifth interspace laterally, and then follows the contour of rib VI anteriorly (see pp. 241–242).
+The  horizontal  fissure  follows  the  fourth  intercostal space from the sternum until it meets the oblique fissure as it crosses rib V.
+The orientations of the oblique and horizontal fissures determine where clinicians should listen for lung sounds from each lobe.
+The largest surface of  the superior lobe is in contact with the upper part of the anterolateral wall and the apex of this lobe projects into the root of the neck. The surface of the middle lobe lies mainly adjacent to the lower anterior
+Regional Anatomy  •  Pleural Cavities	3
+
+
+Right lung	Left lung
+
+Apex Anterior border
+
+Hilum
+
+
+
+
+
+Bronchus
+
+Pulmonary artery
+Pulmonary veins
+
+
+
+Posterior border
+
+
+
+Costal surface	Mediastinal surface
+
+Inferior border
+Base (diaphragmatic surface)
+
+Fig. 3.43  Lungs.
+
+
+
+
+Root
+
+Hilum
+
+Bronchus
+
+
+Pulmonary artery (deoxygenated blood)
+
+Pulmonary veins (oxygenated blood)
+
+
+
+Pulmonary artery
+
+Pulmonary veins
+
+
+
+
+
+
+
+
+
+Pulmonary ligament
+Right lung	Left lung
+
+Fig. 3.44  Roots and hila of the lungs.	171
+Thorax
+
+
+
+
+
+Superior lobe
+
+
+Oblique fissure
+
+Horizontal fissure
+
+
+
+Inferior lobe
+
+Middle lobe
+
+
+
+
+A
+
+Anterior	Subclavian artery	Rib I	Posterior
+
+Subclavian vein
+
+
+
+
+Right brachiocephalic vein
+
+Left brachiocephalic vein
+
+
+
+Superior vena cava
+
+
+Pulmonary artery
+
+
+Pulmonary veins
+
+Heart
+
+
+Bronchus to superior lobe
+
+Bronchus
+
+Esophagus
+
+Azygos vein
+
+
+
+
+
+
+
+
+
+
+
+
+Inferior vena cava
+
+B	Diaphragm
+
+172	Fig. 3.45  A. Right lung. B. Major structures related to the right lung.
+Regional Anatomy  •  Pleural Cavities	3
+
+
+
+and lateral wall. The costal surface of the inferior lobe is in contact with the posterior and inferior walls.
+When listening to lung sounds from each of the lobes, it is important to position the stethoscope on those areas
+
+The medial surface of  the left lung lies adjacent to a number of important structures in the mediastinum and root of the neck (Fig. 3.46B). These include the:
+
+
+
+of the thoracic wall related to the underlying positions of the lobes (see p. 243).
+The medial surface of the right lung lies adjacent to a number of important structures in the mediastinum and the root of the neck (Fig. 3.45B). These include the:
+
+■     heart,
+■     aortic arch,
+■     thoracic aorta, and ■     esophagus.
+
+
+
+
+■     heart,
+■     inferior vena cava, ■     superior vena cava, ■     azygos vein, and
+■     esophagus.
+
+The right subclavian artery and vein arch over and
+
+The left subclavian artery and vein arch over and are related to the superior lobe of the left lung as they pass over the dome of the cervical pleura and into the axilla.
+
+Bronchial tree
+The trachea is a flexible tube that extends from vertebral level CVI in the lower neck to vertebral level TIV/V in the mediastinum where it bifurcates into a right and a left
+
+
+
+are related to the superior lobe of the right lung as they pass over the dome of  the cervical pleura and into the axilla.
+
+Left lung
+The left lung is smaller than the right lung and has two lobes separated by an oblique fissure (Fig. 3.46A). The oblique fissure of the left lung is slightly more oblique than the corresponding fissure of the right lung.
+During quiet respiration, the approximate position of the left oblique fissure can be marked by a curved line on  the  thoracic  wall  that  begins  between  the  spinous processes of vertebrae TIII and TIV, crosses the fifth inter-space laterally, and follows the contour of rib VI anteriorly (see pp. 241–242).
+As with the right lung, the orientation of the oblique fissure determines where to listen for lung sounds from each lobe.
+The largest surface of  the superior lobe is in contact with the upper part of the anterolateral wall, and the apex of this lobe projects into the root of the neck. The costal surface of the inferior lobe is in contact with the posterior and inferior walls.
+When listening to lung sounds from each of the lobes, the stethoscope should be placed on those areas of  the thoracic wall related to the underlying positions of  the lobes (see p. 243).
+The inferior portion of  the medial surface of  the left lung, unlike the right lung, is notched because of  the heart’s  projection  into  the  left  pleural  cavity  from  the middle mediastinum.
+From the anterior border of the lower part of the supe-rior lobe a tongue-like extension (the lingula of the left lung) projects over the heart bulge.
+
+main bronchus (Fig. 3.47). The trachea is held open by C-shaped transverse cartilage rings embedded in its wall— the open part of the C facing posteriorly. The lowest tracheal ring has a hook-shaped structure, the carina, that projects backward in the midline between the origins of the two main bronchi. The posterior wall of the trachea is com-posed mainly of smooth muscle.
+Each main bronchus enters the root of  a lung and passes through the hilum into the lung itself. The right main  bronchus  is  wider  and  takes  a  more  vertical course through the root and hilum than the left main bronchus (Fig. 3.47A). Therefore, inhaled foreign bodies tend to lodge more frequently on the right side than on the left.
+The main bronchus divides within the lung into lobar bronchi (secondary bronchi), each of  which supplies a lobe. On the right side, the lobar bronchus to the superior lobe originates within the root of the lung.
+The  lobar  bronchi  further  divide  into  segmental bronchi (tertiary bronchi), which supply bronchopulmo-nary segments (Fig. 3.47B).
+Within each bronchopulmonary segment, the segmen-tal bronchi give rise to multiple generations of  divisions and, ultimately, to bronchioles, which further subdivide and  supply  the  respiratory  surfaces.  The  walls  of  the bronchi are held open by discontinuous elongated plates of cartilage, but these are not present in bronchioles.
+
+Bronchopulmonary segments
+A  bronchopulmonary  segment  is  the  area  of  lung supplied by a segmental bronchus and its accompanying pulmonary artery branch.
+Tributaries of the pulmonary vein tend to pass interseg-mentally between and around the margins of segments.
+173
+Thorax
+
+
+
+
+
+
+
+
+Superior lobe
+Oblique fissure
+
+
+
+
+
+Inferior lobe
+
+
+
+
+Lingula
+
+
+
+A
+Posterior
+Rib I
+
+
+Anterior
+Left subclavian artery
+
+
+
+Left brachiocephalic vein
+
+
+
+
+
+
+Aortic arch
+
+
+Pulmonary artery
+
+Bronchus
+
+
+
+Esophagus
+
+
+Thoracic aorta
+
+
+
+Pulmonary veins
+
+Heart
+
+
+
+
+
+
+
+
+
+
+
+B	Diaphragm 174
+Fig. 3.46  A. Left lung. B. Major structures related to the left lung.
+Regional Anatomy  •  Pleural Cavities	3
+
+
+
+
+Trachea Right main bronchus
+
+Carina
+
+Left main bronchus
+
+
+
+Lobar bronchi Lobar bronchi
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A
+Segmental bronchi
+of middle lobe
+
+
+
+
+
+
+
+Lateral bronchopulmonary segment of middle lobe of right lung
+Branch of pulmonary artery
+
+
+
+
+
+Medial bronchopulmonary  segment of middle lobe of right lung
+
+B
+
+Fig. 3.47  A. Bronchial tree. B. Bronchopulmonary segments.
+
+
+
+
+
+
+
+
+
+
+175
+Thorax
+
+
+
+Each  bronchopulmonary  segment  is  shaped  like  an irregular cone, with the apex at the origin of the segmental bronchus and the base projected peripherally onto the surface of the lung.
+
+
+Pulmonary arteries
+The  right  and  left  pulmonary  arteries  originate  from the pulmonary trunk and carry deoxygenated blood
+
+A bronchopulmonary segment is the smallest function-ally independent region of a lung and the smallest area of
+
+to  the  lungs  from  the  right  ventricle  of   the  heart (Fig. 3.49).
+
+
+
+lung that can be isolated and removed without affecting adjacent regions.
+There are ten bronchopulmonary segments in each lung (Fig. 3.48); some of them fuse in the left lung.
+
+
+
+
+
+
+Medial view
+
+The  bifurcation  of  the  pulmonary  trunk  occurs  to the left of the midline just inferior to vertebral level TIV/V, and anteroinferiorly to the left of  the bifurcation of  the trachea.
+
+
+
+
+
+
+Lateral view
+
+
+
+
+Apical segment (S I)
+Superior lobe
+
+Anterior segment (S III)
+
+
+Medial segment (S V)
+
+Middle lobe
+
+
+
+Anterior basal segment (S VIII)
+
+A
+
+Posterior segment (S II)
+
+
+
+
+Superior segment (S VI)
+Inferior lobe
+Medial basal segment (S VII)
+
+Posterior basal segment (S X)
+
+
+
+Lateral basal segment (S IX)
+
+
+Apical segment (S I)
+
+
+
+Anterior segment (S III)
+
+
+
+Medial segment (S V)
+
+Lateral segment (S IV)
+Anterior basal segment (S VIII)
+
+
+Apicoposterior segment (S I & II)
+
+
+
+
+
+
+
+Superior segment (S VI)
+
+Inferior lobe
+
+Posterior basal segment (S X)
+
+
+Medial basal segment (S VII)
+
+Superior lobe
+Anterior segment (S III)
+
+Superior lingular segment (S IV)
+
+Inferior lingular segment (S V)
+
+Anterior basal segment (S VIII)
+
+
+
+Superior segment (S VI)
+
+
+Posterior basal segment (S X)
+
+
+B	Lateral basal segment (S IX)
+
+176	Fig. 3.48  Bronchopulmonary segments. A. Right lung. B. Left lung. (Bronchopulmonary segments are numbered and named.)
+Regional Anatomy  •  Pleural Cavities	3
+
+
+
+
+Right pulmonary artery
+The right pulmonary artery is longer than the left and passes horizontally across the mediastinum (Fig. 3.49). It passes:
+
+of the lung, pass through the root of the lung, and imme-diately drain into the left atrium.
+
+Bronchial arteries and veins
+The bronchial arteries (Fig. 3.49) and veins constitute the
+
+
+
+
+■     anteriorly and slightly inferiorly to the tracheal bifur-cation and anteriorly to the right main bronchus, and
+■     posteriorly to the ascending aorta, superior vena cava, and upper right pulmonary vein.
+
+“nutritive”  vascular  system  of  the  pulmonary  tissues (bronchial walls and glands, walls of  large vessels, and visceral pleura). They interconnect within the lung with branches of the pulmonary arteries and veins.
+The bronchial arteries originate from the thoracic aorta or one of its branches:
+
+
+
+The right pulmonary artery enters the root of the lung and gives off  a large branch to the superior lobe of  the lung. The main vessel continues through the hilum of the lung, gives off  a second (recurrent) branch to the superior lobe, and then divides to supply the middle and inferior lobes.
+
+Left pulmonary artery
+The left pulmonary artery is shorter than the right and lies anterior to the descending aorta and posterior to the
+
+
+■     A single right bronchial artery normally arises from the third posterior intercostal artery (but occasionally, it originates from the upper left bronchial artery).
+■     Two left bronchial arteries arise directly from the anterior surface of  the thoracic aorta—the superior left bronchial artery arises at vertebral level TV, and the inferior one inferior to the left bronchus.
+
+The bronchial arteries run on the posterior surfaces of
+
+
+
+superior pulmonary vein (Fig. 3.49). It passes through the root and hilum and branches within the lung.
+
+Pulmonary veins
+
+the bronchi and ramify in the lungs to supply pulmonary tissues.
+The bronchial veins drain into:
+
+
+
+On each side a superior pulmonary vein and an inferior pulmonary vein carry oxygenated blood from the lungs back to the heart (Fig. 3.49). The veins begin at the hilum
+
+■     either the pulmonary veins or the left atrium, and
+■     into the azygos vein on the right or into the superior intercostal vein or hemiazygos vein on the left.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+177
+Thorax
+
+
+
+
+
+
+
+
+
+
+
+
+Right bronchial artery (branch from right third posterior intercostal artery)
+
+
+Aortic arch
+
+Superior left bronchial artery
+
+
+Right pulmonary artery
+
+
+
+
+Bronchial vessels on posterior surface of bronchi
+
+Left pulmonary artery
+Inferior left bronchial artery
+
+
+Left pulmonary veins
+Right pulmonary veins
+
+
+
+Pulmonary trunk	Pulmonary ligament
+Thoracic aorta
+
+
+Esophagus
+
+A
+
+Superior vena cava	Ascending aorta	Pulmonary trunk	Superior vena cava	Ascending aorta	Pulmonary trunk
+
+
+
+
+
+
+
+
+
+
+
+
+
+B	C
+
+
+Right main bronchus	Esophagus	Left pulmonary artery	Right pulmonary artery	Esophagus	Thoracic aorta
+Thoracic aorta
+
+Fig. 3.49  Pulmonary vessels. A. Diagram of an anterior view. B. Axial computed tomography image showing the left pulmonary artery branching from the pulmonary trunk. C. Axial computed tomography image (just inferior to the image in B) showing the right pulmonary artery
+178	branching from the pulmonary trunk.
+Regional Anatomy  •  Pleural Cavities	3
+
+
+
+
+Innervation
+Structures of the lung and the visceral pleura are supplied by  visceral  afferents  and  efferents  distributed  through
+
+Visceral efferents from:
+
+■     the vagus nerves constrict the bronchioles;
+■     the sympathetic system dilates the bronchioles.
+
+
+
+the anterior pulmonary plexus and posterior pulmonary plexus (Fig. 3.50). These interconnected plexuses lie ante-riorly and posteriorly to the tracheal bifurcation and main bronchi. The anterior plexus is much smaller than the posterior plexus.
+Branches of these plexuses, which ultimately originate from the sympathetic trunks and vagus nerves, are distrib-uted along branches of the airway and vessels.
+
+
+Lymphatic drainage
+Superficial, or subpleural, and deep lymphatics of the lung drain into lymph nodes called tracheobronchial nodes around the roots of lobar and main bronchi and along the sides of the trachea (Fig. 3.51). As a group, these lymph nodes extend from within the lung, through the hilum and root, and into the posterior mediastinum.
+
+
+
+
+
+
+
+
+
+
+Cervical cardiac nerves
+
+
+
+
+
+Left recurrent laryngeal nerve
+
+
+Left vagus nerve Right vagus nerve
+
+
+Ligamentum arteriosum Anterior pulmonary plexus
+
+
+
+
+
+
+
+
+Posterior pulmonary plexus	Sympathetic trunk
+
+Esophageal plexus
+
+
+
+
+
+
+
+
+Fig. 3.50  Pulmonary innervation.	179
+Thorax
+
+
+Thoracic duct
+
+Brachiocephalic node
+
+Right bronchomediastinal trunk
+
+
+Left bronchomediastinal trunk
+
+
+Left parasternal lymphatic vessel
+
+Right parasternal lymphatic vessel
+
+
+
+
+
+Tracheobronchial nodes	Parasternal nodes
+
+
+
+
+
+
+
+
+
+Thoracic duct
+
+
+
+
+
+
+
+
+
+Diaphragm
+
+
+Cisterna chyli
+
+
+
+
+
+
+
+
+Fig. 3.51  Lymphatic drainage of lungs.
+
+
+
+
+
+180
+Regional Anatomy  •  Pleural Cavities	3
+
+
+
+Efferent vessels from these nodes pass superiorly along the trachea to unite with similar vessels from parasternal nodes and brachiocephalic nodes, which are anterior to brachiocephalic  veins  in  the  superior  mediastinum,  to form the right and left bronchomediastinal trunks. These trunks drain directly into deep veins at the base of the neck, or may drain into the right lymphatic trunk or tho-racic duct.
+
+
+In the clinic
+
+Imaging the lungs
+Medical imaging of the lungs is important because they are one of the commonest sites for disease in the body. While the body is at rest, the lungs exchange up to 5 L of air per minute, and this may contain pathogens and other potentially harmful elements (e.g., allergens). Techniques to visualize the lung range from plain chest radiographs to high-resolution computed tomography (CT), which enables precise localization of a lesion within the lung.
+
+
+
+
+
+
+
+
+
+In the clinic
+
+High-resolution lung CT	Aorta High-resolution computed tomography (HRCT) is a diagnostic
+method for assessing the lungs but more specifically the interstitium of the lungs. The technique involves obtaining narrow cross-sectional slices of 1 to 2 mm. These scans enable the physician and radiologist to view the patterns of disease and their distribution. Diseases that may be easily demonstrated using this procedure include emphysema (Fig. 3.52), pneumoconiosis (coal worker’s pneumoconiosis), and asbestosis. HRCT is also useful in regular follow-ups of patients with interstitial disease to monitor disease progression.
+
+
+
+Emphysematous change in left lung
+
+
+
+
+Emphysematous
+change in right lung	Trachea
+
+Fig. 3.52  HRCT of patient with emphysema.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+181
+Thorax
+
+
+
+In the clinic
+
+Bronchoscopy
+Patients who have an endobronchial lesion (i.e.,
+a lesion within a bronchus) may undergo bronchoscopic evaluation of the trachea and its main branches (Fig. 3.53). The bronchoscope is passed through the nose into the oropharynx and is then directed by a control system past the vocal cords into the trachea. The bronchi are inspected and, if necessary, small biopsies are obtained. Bronchoscopy can
+
+
+
+also be used in combination with ultrasound (a technique known as EBUS, endobronchial ultrasound). An ultrasound probe is inserted through a working channel of the bronchoscope to visualize the airway walls and adjacent structures. EBUS allows an accurate localization of the lesion and therefore provides a higher diagnostic yield. It can be used for sampling of mediastinal and hilar lymph nodes or to assist in transbronchial biopsy of pulmonary nodules.
+
+
+
+Carina	Right main bronchus	Right main bronchus
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A	B
+
+Left main bronchus	Tumor
+
+Fig. 3.53  Bronchoscopic evaluation. A. Of the lower end of the trachea and its main branches. B. Of tracheal bifurcation showing a tumor at the carina.
+
+
+
+
+
+
+In the clinic
+
+Lung cancer
+It is important to stage lung cancer because the treatment depends on its stage.
+If a small malignant nodule is found within the lung, it can sometimes be excised and the prognosis is excellent. Unfortunately, many patients present with a tumor mass that has invaded structures in the mediastinum or the pleurae or has metastasized. The tumor may then be inoperable and is treated with radiotherapy and chemotherapy.
+Spread of the tumor is by lymphatics to lymph nodes within the hila, mediastinum, and root of the neck.
+
+182
+
+
+
+A key factor affecting the prognosis and ability to cure the disease is the distant spread of metastases. Imaging methods to assess spread include plain radiography (Fig. 3.54A), computed tomography (CT; Fig. 3.54B,C), and magnetic resonance imaging (MRI). Increasingly, radionuclide studies using fluorodeoxyglucose positron emission tomography (FDG PET; Fig. 3.54D) are being used.
+In FDG PET a gamma radiation emitter is attached to a glucose molecule. In areas of high metabolic activity (i.e., the tumor), excessive uptake occurs and is recorded by a gamma camera.
+Regional Anatomy  •  Pleural Cavities	3
+
+
+In the clinic—cont’d
+
+Right lung	Lung cancer Tumor
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A	C
+Rib	Ascending aorta
+Tumor
+
+
+Pulmonary trunk
+Tumor
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+B
+
+
+
+D
+
+Fig. 3.54  Imaging of the lungs. A. Standard posteroanterior view of the chest showing tumor in upper right lung. B. Axial CT image of lungs showing tumor in right lung. C. Coronal CT image of lungs showing tumor in left lung extending into mediastinum. D. Radionuclide study using FDG PET showing a tumor in the right lung.
+
+
+
+
+
+
+
+
+
+183
+Thorax
+
+
+
+MEDIASTINUM
+
+The mediastinum is a broad central partition that sepa-rates the two laterally placed pleural cavities (Fig. 3.55). It extends:
+
+The area anterior to the pericardial sac and posterior to the body of the sternum is the anterior mediastinum. The region posterior to the pericardial sac and the diaphragm and anterior to the bodies of the vertebrae is the posterior mediastinum. The area in the middle, which includes the
+
+
+
+
+■     from the sternum to the bodies of the vertebrae, and
+■     from the superior thoracic aperture to the diaphragm (Fig. 3.56).
+
+The mediastinum contains the thymus gland, the peri-
+
+pericardial sac and its contents, is the middle mediastinum (Fig. 3.57).
+
+Anterior mediastinum
+The anterior mediastinum is posterior to the body of the sternum and anterior to the pericardial sac (see Fig. 3.57).
+
+
+
+cardial sac, the heart, the trachea, and the major arteries and veins.
+Additionally, the mediastinum serves as a passageway for structures such as the esophagus, thoracic duct, and various components of the nervous system as they traverse the thorax on their way to the abdomen.
+For organizational purposes, the mediastinum is subdi-vided  into  several  smaller  regions.  A  transverse  plane extending from the sternal angle (the junction between the manubrium and the body of the sternum) to the interver-tebral disc between vertebrae TIV and TV separates the mediastinum into the:
+
+
+■     Its  superior  boundary  is  a  transverse  plane  passing from the sternal angle to the intervertebral disc between vertebra TIV and TV, separating it from the superior mediastinum.
+
+
+Superior thoracic aperture
+
+
+
+
+I
+
+
+
+
+■     superior mediastinum, and
+■     inferior mediastinum, which is further partitioned into  the  anterior,  middle,  and  posterior  media-stinum by the pericardial sac.
+
+II
+
+Sternal angle	III
+
+IV
+
+V
+Sternum	VI
+
+Mediastinum	Left pleural cavity	VII
+
+VIII
+
+IX
+
+X
+
+XI
+
+XII
+
+
+
+
+Diaphragm
+
+
+
+
+
+
+Right pleural cavity
+
+Fig. 3.55  Cross-section of the thorax showing the position of the
+184	mediastinum.	Fig. 3.56  Lateral view of the mediastinum.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+
+Sternal angle
+I
+
+II
+
+Superior	III mediastinum                                                            IV
+
+posterior surface of the body of the sternum to the fibrous pericardium.
+
+Middle mediastinum
+The  middle  mediastinum  is  centrally  located  in  the thoracic cavity. It contains the pericardium, heart, origins of the great vessels, various nerves, and smaller vessels.
+
+
+
+Anterior	V mediastinum	VI
+
+Inferior                                                             VII mediastinum                                                            VIII
+
+IX
+
+X
+
+XI
+
+Middle mediastinum	XII
+
+
+Pericardium
+The pericardium is a fibroserous sac surrounding the heart and the roots of the great vessels. It consists of two components, the fibrous pericardium and the serous peri-cardium (Fig. 3.59).
+The fibrous pericardium is a tough connective tissue outer  layer  that  defines  the  boundaries  of  the  middle mediastinum. The serous pericardium is thin and con-sists of two parts:
+
+■     The parietal  layer of  serous pericardium lines the inner surface of the fibrous pericardium.
+
+■     The visceral layer (epicardium) of  serous pericar-dium  adheres  to  the  heart  and  forms  its  outer
+
+Posterior mediastinum
+
+
+
+
+
+
+Fig. 3.57  Subdivisions of the mediastinum.
+
+covering.
+
+The parietal and visceral layers of serous pericardium are continuous at the roots of the great vessels. The narrow space created between the two layers of  serous pericar-dium, containing a small amount of fluid, is the pericar-dial cavity. This potential space allows for the relatively uninhibited movement of the heart.
+
+
+
+
+■     Its inferior boundary is the diaphragm.
+■     Laterally, it is bordered by the mediastinal part of pari-etal pleura on either side.
+
+The major structure in the anterior mediastinum is
+
+Fibrous pericardium
+The fibrous pericardium is a cone-shaped bag with its base on the diaphragm and its apex continuous with the adventitia of  the great vessels (Fig. 3.59). The base is attached to the central tendon of the diaphragm and to a small muscular area of the diaphragm on the left side.
+
+
+
+an inferior extension of  the thymus gland (Fig. 3.58). Also  present  are  fat,  connective  tissue,  lymph  nodes,
+
+Anteriorly, it is attached to the posterior surface of  the sternum by sternopericardial ligaments. These attach-
+
+mediastinal  branches  of  the  internal  thoracic  vessels,	ments help to retain the heart in its position in the thoracic and  sternopericardial  ligaments,  which  pass  from  the	cavity. The sac also limits cardiac distention.
+
+
+
+
+
+
+
+
+
+
+
+185
+Thorax
+
+
+
+
+
+
+
+
+Right internal thoracic artery	Left internal thoracic artery
+
+
+
+TIV/V vertebral level
+
+
+
+
+Thymus
+
+Pericardial sac
+
+
+
+
+
+
+
+
+Fig. 3.58  Thymus.
+
+
+
+
+
+
+
+Junction between fibrous pericardium and adventitia of great vessels
+
+Visceral layer of serous pericardium (epicardium)
+
+Pericardial cavity
+
+
+
+
+
+
+
+
+
+
+Parietal layer of serous pericardium
+
+
+Fibrous pericardium
+
+
+186	Fig. 3.59  Sagittal section of the pericardium.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+The phrenic nerves, which innervate the diaphragm and originate from spinal cord levels C3 to C5, pass through the fibrous pericardium and innervate the fibrous pericar-dium as they travel from their point of origin to their final destination (Fig. 3.60). Their location, within the fibrous pericardium, is directly related to the embryological origin of  the  diaphragm  and  the  changes  that  occur  during
+
+pericardiacophrenic vessels are also located within and supply the fibrous pericardium as they pass through the thoracic cavity.
+
+
+Serous pericardium
+The parietal layer of serous pericardium is continuous with
+
+the  formation  of  the  pericardial  cavity.  Similarly,  the	the visceral layer of serous pericardium around the roots
+
+
+
+
+
+
+Trachea
+Left common carotid artery
+
+
+
+
+
+
+
+
+
+Superior vena cava	Left phrenic nerve
+
+
+
+Right phrenic nerve
+
+
+Left pericardiacophrenic vessels
+
+
+
+
+
+
+
+
+Right pericardiacophrenic vessels
+
+Diaphragm	Pericardium
+
+
+
+
+Fig. 3.60  Phrenic nerves and pericardiacophrenic vessels.
+
+
+
+
+
+
+187
+Thorax
+
+
+
+of the great vessels. These reflections of serous pericardium (Fig. 3.61) occur in two locations:
+
+arteries from veins. A hand placed under the apex of the heart and moved superiorly slips into the oblique sinus.
+
+
+
+■     one superiorly, surrounding the arteries—the aorta and the pulmonary trunk;
+■     the second more posteriorly, surrounding the veins—the superior and inferior vena cava and the pulmonary veins.
+
+Vessels and nerves
+The pericardium is supplied by branches from the internal thoracic, pericardiacophrenic, musculophrenic, and infe-rior phrenic arteries, and the thoracic aorta.
+Veins from the pericardium enter the azygos system of veins and the internal thoracic and superior phrenic veins.
+
+The zone of reflection surrounding the veins is J-shaped,	Nerves  supplying  the  pericardium  arise  from  the
+
+and the cul-de-sac formed within the J, posterior to the left atrium, is the oblique pericardial sinus.
+A passage between the two sites of  reflected serous pericardium is the transverse pericardial sinus. This sinus lies posterior to the ascending aorta and the pulmo-nary trunk, anterior to the superior vena cava, and superior to the left atrium.
+When  the  pericardium  is  opened  anteriorly  during surgery, a finger placed in the transverse sinus separates
+
+
+vagus nerve [X], the sympathetic trunks, and the phrenic nerves.
+It is important to note that the source of somatic sensa-tion (pain) from the parietal pericardium is carried by somatic  afferent  fibers  in  the  phrenic  nerves.  For  this reason, “pain” related to a pericardial problem may be referred to the supraclavicular region of the shoulder or lateral neck area dermatomes for spinal cord segments C3, C4, and C5.
+
+
+
+
+
+
+
+
+Superior vena cava
+
+
+
+Ascending aorta
+
+
+Transverse pericardial sinus (separates arteries from veins)
+
+Arch of aorta
+
+
+
+Left pulmonary artery
+
+
+Branch of right pulmonary artery
+Left pulmonary veins
+
+
+Right pulmonary veins
+
+
+Oblique pericardial sinus (formed by reflection onto the pulmonary veins of heart)
+
+
+
+Cut edge of pericardium
+
+Inferior vena cava
+
+
+Thoracic aorta
+
+
+188	Fig. 3.61  Posterior portion of pericardial sac showing reflections of serous pericardium.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+In the clinic
+
+Pericarditis
+Pericarditis is an inflammatory condition of the pericardium. Common causes are viral and bacterial infections, systemic illnesses (e.g., chronic renal failure), and after myocardial infarction.
+Pericarditis must be distinguished from myocardial infarction because the treatment and prognosis are quite different. As in patients with myocardial infarction, patients
+
+
+
+
+
+In the clinic
+
+Pericardial effusion
+Normally, only a tiny amount of fluid is present between the visceral and parietal layers of the serous pericardium. In certain situations, this space can be filled with excess fluid (pericardial effusion) (Fig. 3.62).
+Because the fibrous pericardium is a “relatively fixed” structure that cannot expand easily, a rapid accumulation of excess fluid within the pericardial sac compresses the heart (cardiac tamponade), resulting in biventricular failure. Removing the fluid with a needle inserted into the pericardial sac can relieve the symptoms.
+
+Ascending aorta	Pulmonary trunk
+Right lung	Left lung
+
+
+
+with pericarditis complain of continuous central chest pain that may radiate to one or both arms. Unlike myocardial infarction, however, the pain from pericarditis may be relieved by sitting forward. An electrocardiogram (ECG) is used to help differentiate between the two conditions. It usually shows diffuse ST elevation. Echocardiography can also be performed if there is clinical or radiographic suspicion of pericardial effusion.
+
+
+
+
+
+In the clinic
+
+Constrictive pericarditis
+Abnormal thickening of the pericardial sac (constrictive pericarditis), which usually involves only the parietal pericardium, but can also less frequently involve the visceral layer, can compress the heart, impairing heart function and resulting in heart failure. It can present acutely but often results in a chronic condition when thickened pericardium with fibrin deposits causes pericardial inflammation, leading to chronic scarring and pericardial calcification. As a result, normal filling during the diastolic phase of the cardiac cycle is severely restricted. The diagnosis is made by inspecting the jugular venous pulse in the neck. In normal individuals, the jugular venous pulse drops on inspiration. In patients with constrictive pericarditis, the reverse happens and this is called Kussmaul’s sign. Treatment often involves surgical opening of the pericardial sac.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Liver
+Stomach
+
+Pericardial effusion
+
+
+Fig. 3.62  Coronal CT showing pericardial effusion.
+
+
+
+189
+Thorax
+
+
+
+Heart
+Cardiac orientation
+The general shape and orientation of the heart are that of a pyramid that has fallen over and is resting on one of its sides. Placed in the thoracic cavity, the apex of this pyramid projects forward, downward, and to the left, whereas the base is opposite the apex and faces in a posterior direction (Fig. 3.63). The sides of the pyramid consist of:
+
+
+Anterior surface
+
+
+
+Base
+
+
+
+
+
+
+
+
+Left pulmonary surface
+
+
+■     a   diaphragmatic   (inferior)   surface   on   which   the pyramid rests,
+■     an anterior (sternocostal) surface oriented anteriorly,
+■     a right pulmonary surface, and                                                                                                                                Obtuse ■     a left pulmonary surface.                                                                                                                                           margin
+
+
+
+Base (posterior surface) and apex
+The base of the heart is quadrilateral and directed pos-teriorly. It consists of:
+
+Right pulmonary surface
+
+
+Apex
+
+Inferior (acute) margin
+
+
+
+■     the left atrium,
+■     a small portion of the right atrium, and
+■     the proximal parts of the great veins (superior and infe-rior venae cavae and the pulmonary veins) (Fig. 3.64).
+
+Diaphragmatic surface
+
+
+Fig. 3.63  Schematic illustration of the heart showing orientation, surfaces, and margins.
+
+
+
+
+
+
+Arch of aorta Left pulmonary artery
+Superior vena cava
+
+Left superior pulmonary vein
+
+Right pulmonary artery
+
+
+Left atrium
+
+Right pulmonary veins
+Left inferior pulmonary vein
+
+Right atrium
+
+Coronary sinus	Sulcus terminalis
+
+
+Left ventricle
+
+Inferior vena cava
+
+
+Apex	Right ventricle
+
+
+190	Fig. 3.64  Base of the heart.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+Because the great veins enter the base of the heart, with the pulmonary veins entering the right and left sides of the left atrium and the superior and inferior venae cavae at the upper and lower ends of the right atrium, the base of  the heart is fixed posteriorly to the pericardial wall, opposite the bodies of vertebrae TV to TVIII (TVI to TIX when standing). The esophagus lies immediately posterior to the base.
+
+From the base the heart projects forward, downward, and to the left, ending in the apex. The apex of the heart is formed by the inferolateral part of  the left ventricle (Fig. 3.65) and is positioned deep to the left fifth intercostal space, 8 to 9 cm from the midsternal line.
+
+
+
+
+
+
+
+Aorta	Pulmonary trunk
+
+
+
+Pulmonary valve
+
+Aortic valve
+
+RA
+
+
+Superior vena cava
+Arch of aorta
+
+
+LA	Bicuspid valve
+
+
+
+Ascending aorta	Tricuspid valve	RV
+LV Pulmonary trunk
+
+
+
+Right coronary artery
+
+
+Right atrium
+
+
+Right ventricle
+
+Left auricle
+
+
+Anterior interventricular branch of left coronary artery
+
+Great cardiac vein
+
+Anterior interventricular groove
+
+Left ventricle
+
+
+
+Obtuse margin
+Small cardiac vein
+
+Inferior vena cava
+
+Apex
+Inferior margin
+
+Fig. 3.65  Anterior surface of the heart.
+
+
+
+
+
+
+
+
+191
+Thorax
+
+
+Surfaces of the heart                                                                             The right pulmonary surface faces the right lung, The  anterior  surface  faces  anteriorly  and  consists       is broad and convex, and consists of  the right atrium
+
+mostly  of  the  right  ventricle,  with  some  of  the  right atrium on the right and some of the left ventricle on the left (Fig. 3.65).
+The heart in the anatomical position rests on the dia-phragmatic surface, which consists of the left ventricle
+
+(Fig. 3.66).
+
+Margins and borders
+Some general descriptions of cardiac orientation refer to right, left, inferior (acute), and obtuse margins:
+
+
+
+and a small portion of the right ventricle separated by the posterior interventricular groove (Fig. 3.66). This surface faces inferiorly, rests on the diaphragm, is separated from the base of the heart by the coronary sinus, and extends from the base to the apex of the heart.
+The left pulmonary surface faces the left lung, is broad and convex, and consists of the left ventricle and a portion of the left atrium (Fig. 3.66).
+
+
+■     The right and left margins are the same as the right and left pulmonary surfaces of the heart.
+■     The  inferior  margin  is  defined  as  the  sharp  edge between the anterior and diaphragmatic surfaces of the heart (Figs 3.63 and 3.65)—it is formed mostly by the right ventricle and a small portion of the left ventricle near the apex.
+
+
+
+
+
+
+
+
+
+Arch of aorta
+
+Left pulmonary artery
+
+Superior vena cava
+
+
+Right pulmonary artery
+
+Left pulmonary veins
+
+Right pulmonary veins
+
+Left atrium
+Right atrium
+
+Coronary sinus
+
+Inferior vena cava
+
+
+Left ventricle
+Marginal branch of right coronary artery
+
+
+Posterior interventricular branch of right coronary artery
+
+
+Apex
+
+
+Right ventricle
+
+
+Middle cardiac vein
+
+Posterior interventricular groove
+
+
+192	Fig. 3.66  Diaphragmatic surface of the heart.
+Regional Anatomy  •  Mediastinum	3
+
+
+■     The obtuse  margin separates the anterior and left pulmonary surfaces (Fig. 3.63)—it is round and extends from the left auricle to the cardiac apex (Fig. 3.65), and is formed mostly by the left ventricle and superiorly by
+
+External sulci
+Internal partitions divide the heart into four chambers (i.e., two atria and two ventricles) and produce surface or external grooves referred to as sulci.
+
+a small portion of the left auricle.
+
+
+For radiological evaluations, a thorough understanding of  the structures defining the cardiac borders is critical. The right border in a standard posteroanterior view con-sists of the superior vena cava, the right atrium, and the inferior vena cava (Fig. 3.67A). The left border in a similar view consists of  the arch of  the aorta, the pulmonary trunk, left auricle, and the left ventricle. The inferior border in this radiological study consists of the right ventricle and the left ventricle at the apex. In lateral views, the right ventricle is seen anteriorly, and the left atrium is visualized posteriorly (Fig. 3.67B).
+
+
+■     The coronary sulcus circles the heart, separating the atria from the ventricles (Fig. 3.68). As it circles the heart, it contains the right coronary artery, the small cardiac vein, the coronary sinus, and the circumflex branch of the left coronary artery.
+■     The anterior and posterior interventricular sulci separate the two ventricles—the anterior interventricu-lar sulcus is on the anterior surface of the heart and contains the anterior interventricular artery and the great cardiac vein, and the posterior interventricular sulcus is on the diaphragmatic surface of the heart and contains the posterior interventricular artery and the middle cardiac vein.
+
+
+
+
+
+
+
+
+
+
+Arch of aorta  Pulmonary trunk
+
+Inferior vena cava
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A
+
+Right atrium
+Superior vena cava
+
+Left auricle
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Apex of heart
+Left ventricle
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+B
+
+Right ventricle	Left atrium
+
+
+Fig. 3.67  Chest radiographs. A. Standard posteroanterior view of the chest. B. Standard lateral view of the heart.	193
+Thorax
+
+
+
+
+
+
+
+
+
+Great cardiac vein
+
+
+
+Coronary sulcus
+
+
+
+Right coronary artery
+
+Anterior interventricular sulcus
+
+
+Anterior interventricular branch Small cardiac vein	of left coronary artery
+
+A
+
+
+
+
+
+
+
+
+
+
+Great cardiac vein
+
+
+Circumflex branch of left coronary artery
+
+
+Coronary sulcus	Small cardiac vein
+
+
+Coronary sinus
+
+Right coronary artery
+
+
+
+Middle cardiac vein	Posterior interventricular sulcus
+
+
+B
+
+Posterior interventricular branch of right coronary artery
+
+
+Fig. 3.68  Sulci of the heart. A. Anterior surface of the heart. B. Diaphragmatic surface and base of the heart.
+
+
+194
+Regional Anatomy  •  Mediastinum	3
+
+
+
+These sulci are continuous inferiorly, just to the right of the apex of the heart.
+
+Cardiac chambers
+The heart functionally consists of two pumps separated by a partition (Fig. 3.69A). The right pump receives deoxy-genated blood from the body and sends it to the lungs. The left pump receives oxygenated blood from the lungs and
+
+The thin-walled atria receive blood coming into the heart, whereas the relatively thick-walled ventricles pump blood out of the heart.
+More force is required to pump blood through the body than through the lungs, so the muscular wall of the left ventricle is thicker than the right.
+Interatrial, interventricular, and atrioventricular septa separate the four chambers of the heart (Fig. 3.69B). The
+
+
+
+sends it to the body. Each pump consists of an atrium and a ventricle separated by a valve.
+
+internal  anatomy  of   each  chamber  is  critical  to  its function.
+
+
+
+
+
+
+
+Pulmonary arteries
+
+Deoxygenated blood
+
+Superior vena cava
+
+Deoxygenated blood
+
+Left atrium	Aorta
+
+Oxygenated blood
+
+
+
+
+
+Right atrium
+
+Right pump
+LUNGS
+Valve
+
+Left pump
+Left ventricle
+
+
+
+
+
+GENERAL BODY
+
+
+
+
+
+
+Pulmonary veins	Right ventricle
+
+Oxygenated blood
+
+Inferior vena cava
+
+Deoxygenated blood A
+
+
+
+
+
+Right ventricle
+Left ventricle
+Right atrium
+
+Left atrium
+
+Thoracic aorta
+
+
+
+B
+
+
+Fig. 3.69  A. The heart has two pumps. B. Magnetic resonance image of midthorax showing all four chambers and septa.	195
+Thorax
+
+
+
+Right atrium
+In the anatomical position, the right border of the heart is formed by the right atrium. This chamber also contributes to the right portion of the heart’s anterior surface.
+Blood returning to the right atrium enters through one of three vessels. These are:
+
+
+opening faces forward and medially and is closed during ventricular contraction by the tricuspid valve.
+The interior of  the right atrium is divided into two continuous spaces. Externally, this separation is indicated by  a  shallow,  vertical  groove  (the  sulcus  terminalis cordis), which extends from the right side of the opening
+
+
+
+
+■     the superior and inferior venae cavae, which together deliver blood to the heart from the body; and
+■     the coronary sinus, which returns blood from the walls of the heart itself.
+
+The  superior  vena  cava  enters  the  upper  posterior
+
+of the superior vena cava to the right side of the opening of the inferior vena cava. Internally, this division is indi-cated by the crista terminalis (Fig. 3.70), which is a smooth, muscular ridge that begins on the roof  of  the atrium just in front of the opening of the superior vena cava and extends down the lateral wall to the anterior lip of the inferior vena cava.
+
+
+
+portion of the right atrium, and the inferior vena cava and coronary sinus enter the lower posterior portion of  the right atrium.
+From the right atrium, blood passes into the right ven-tricle through the right atrioventricular orifice. This
+
+The space posterior to the crista is the sinus of venae cavae and is derived embryologically from the right horn of the sinus venosus. This component of the right atrium has smooth, thin walls, and both venae cavae empty into this space.
+
+
+
+
+
+
+
+
+Arch of aorta
+
+
+
+
+
+
+Superior vena cava	Right auricle
+
+
+Limbus of fossa ovalis
+
+
+
+Crista terminalis	Right ventricle
+
+
+Musculi pectinati
+
+
+Fossa ovalis
+
+
+Inferior vena cava
+
+
+Valve of inferior vena cava                             Opening of coronary sinus Valve of coronary sinus
+
+196	Fig. 3.70  Internal view of right atrium.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+The space anterior to the crista, including the right auricle, is sometimes referred to as the atrium proper. This terminology is based on its origin from the embryonic primitive atrium. Its walls are covered by ridges called the musculi pectinati (pectinate muscles), which fan out from the crista like the “teeth of  a comb.” These ridges are also found in the right auricle, which is an ear-like, conical,  muscular  pouch  that  externally  overlaps  the ascending aorta.
+An  additional  structure  in  the  right  atrium  is  the opening of  the coronary sinus, which receives blood from most of the cardiac veins and opens medially to the
+
+trabeculae carneae (Fig. 3.71). Most of these are either attached to the ventricular walls throughout their length, forming ridges, or attached at both ends, forming bridges. A few trabeculae carneae (papillary muscles) have only one end attached to the ventricular surface, while the other end serves as the point of attachment for tendon-like fibrous cords (the chordae tendineae), which connect to
+the free edges of the cusps of the tricuspid valve.
+There are three papillary muscles in the right ventricle. Named relative to their point of origin on the ventricular surface, they are the anterior, posterior, and septal papil-lary muscles:
+
+
+
+opening of  the inferior vena cava. Associated with these openings are small folds of tissue derived from the valve of the embryonic sinus venosus (the valve of  the coronary sinus and the valve of  inferior vena cava, respectively). During development, the valve of the inferior vena cava helps direct incoming oxygenated blood through the foramen ovale and into the left atrium.
+Separating the right atrium from the left atrium is the interatrial septum, which faces forward and to the right because the left atrium lies posteriorly and to the left of the right atrium. A depression is clearly visible in the septum just above the orifice of the inferior vena cava. This is the fossa ovalis (oval fossa), with its prominent margin, the
+
+
+■     The anterior papillary muscle is the largest and most constant papillary muscle, and arises from the anterior wall of the ventricle.
+■     The posterior papillary muscle may consist of one, two, or three structures, with some chordae tendineae arising directly from the ventricular wall.
+■     The septal papillary muscle is the most inconsistent papillary   muscle,   being   either   small   or   absent, with  chordae  tendineae  emerging  directly  from  the septal wall.
+
+A single specialized trabeculum, the septomarginal
+
+
+
+limbus fossa ovalis (border of the oval fossa).
+The fossa ovalis marks the location of the embryonic foramen ovale, which is an important part of fetal circu-lation. The foramen ovale allows oxygenated blood enter-ing the right atrium through the inferior vena cava to pass directly to the left atrium and so bypass the lungs, which are nonfunctional before birth.
+Finally, numerous small openings—the openings of the smallest cardiac veins (the foramina of the venae cordis minimae)—are scattered along the walls of  the right atrium. These are small veins that drain the myocar-dium directly into the right atrium.
+
+Right ventricle
+In the anatomical position, the right ventricle forms most of the anterior surface of the heart and a portion of the diaphragmatic surface. The right atrium is to the right of the right ventricle and the right ventricle is located in front of and to the left of the right atrioventricular orifice. Blood entering the right ventricle from the right atrium therefore moves in a horizontal and forward direction.
+
+trabecula (moderator band), forms a bridge between the lower portion of the interventricular septum and the base of the anterior papillary muscle. The septomar-ginal trabecula carries a portion of the cardiac conduction system, the right bundle of the atrioventricular bundle, to the anterior wall of the right ventricle.
+
+Tricuspid valve
+The right atrioventricular orifice is closed during ventricu-lar contraction by the tricuspid valve (right atrioven-tricular valve), so named because it usually consists of three cusps or leaflets (Fig. 3.71). The base of each cusp is secured to the fibrous ring that surrounds the atrioven-tricular orifice. This fibrous ring helps to maintain the shape of the opening. The cusps are continuous with each other near their bases at sites termed commissures.
+The naming of the three cusps, the anterior, septal, and posterior cusps, is based on their relative position in the  right  ventricle. The  free  margins  of  the  cusps  are attached to the chordae tendineae, which arise from the tips of the papillary muscles.
+
+The outflow tract of the right ventricle, which leads to	During  filling  of   the  right  ventricle,  the  tricuspid
+
+the pulmonary trunk, is the conus arteriosus (infun-dibulum). This area has smooth walls and derives from the embryonic bulbus cordis.
+The walls of  the inflow portion of  the right ventricle have  numerous  muscular,  irregular  structures  called
+
+valve is open, and the three cusps project into the right ventricle.
+Without the presence of a compensating mechanism, when the ventricular musculature contracts, the valve
+cusps would be forced upward with the flow of blood and	197
+Thorax
+
+
+
+
+
+
+Superior vena cava	Arch of aorta
+
+
+Pulmonary trunk
+
+
+
+Right auricle
+
+
+
+Right atrium
+
+Left auricle
+
+Anterior semilunar cusp Right semilunar cusp
+Left semilunar cusp
+
+
+
+Pulmonary valve
+
+
+
+Conus arteriosus
+
+
+Tricuspid valve
+
+Anterior cusp Septal cusp Posterior cusp
+
+
+Septal papillary muscle
+
+
+Septomarginal trabecula
+
+
+
+Chordae tendineae
+
+
+Anterior papillary muscle	Posterior papillary muscle
+
+Trabeculae carneae
+
+Fig. 3.71  Internal view of the right ventricle.
+
+
+
+
+blood would move back into the right atrium. However, contraction of the papillary muscles attached to the cusps by chordae tendineae prevents the cusps from being everted into the right atrium.
+
+is  closed  by  the  pulmonary  valve  (Fig.  3.71),  which consists of  three semilunar cusps with free edges pro-jecting upward into the lumen of the pulmonary trunk. The free superior edge of each cusp has a middle, thick-
+
+Simply  put,  the  papillary  muscles  and  associated	ened portion, the nodule of  the semilunar cusp, and
+
+chordae  tendineae  keep  the  valves  closed  during  the dramatic changes in ventricular size that occur during contraction.
+In  addition,  chordae  tendineae  from  two  papillary muscles attach to each cusp. This helps prevent separation of the cusps during ventricular contraction. Proper closing of the tricuspid valve causes blood to exit the right ventricle and move into the pulmonary trunk.
+Necrosis of a papillary muscle following a myocardial infarction (heart attack) may result in prolapse of  the related valve.
+
+Pulmonary valve
+At the apex of the infundibulum, the outflow tract of the right ventricle, the opening into the pulmonary trunk
+198
+
+a thin lateral portion, the lunula of the semilunar cusp (Fig. 3.72).
+The cusps are named the left, right, and anterior semilunar cusps, relative to their fetal position before rotation of the outflow tracts from the ventricles is com-plete. Each cusp forms a pocket-like sinus (Fig. 3.72)—a dilation in the wall of the initial portion of the pulmonary trunk. After ventricular contraction, the recoil of blood fills these pulmonary sinuses and forces the cusps closed. This prevents blood in the pulmonary trunk from refilling the right ventricle.
+
+Left atrium
+The left atrium forms most of the base or posterior surface of the heart.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Nodule Pulmonary sinus
+
+
+
+
+
+
+
+
+Left	Anterior	Right
+Semilunar cusps
+
+
+
+
+
+Nodule
+
+
+
+
+Pulmonary sinus
+
+
+
+Lunule
+
+Left ventricle
+The left ventricle lies anterior to the left atrium. It contrib-utes to the anterior, diaphragmatic, and left pulmonary surfaces of the heart, and forms the apex.
+Blood enters the ventricle through the left atrioven-tricular orifice and flows in a forward direction to the apex. The chamber itself is conical, is longer than the right ventricle, and has the thickest layer of myocardium. The outflow tract (the aortic vestibule) is posterior to the infundibulum of the right ventricle, has smooth walls, and is derived from the embryonic bulbus cordis.
+The trabeculae carneae in the left ventricle are fine and delicate in contrast to those in the right ventricle. The general appearance of the trabeculae with muscular ridges and bridges is similar to that of the right ventricle (Fig. 3.74).
+Papillary muscles, together with chordae tendineae, are also observed and their structure is as described above for the right ventricle. Two papillary muscles, the anterior and posterior papillary muscles, are usually found in the left ventricle and are larger than those of  the right ventricle.
+
+
+
+
+Fig. 3.72  Posterior view of the pulmonary valve.
+
+In the anatomical position, the left ventricle is somewhat posterior to the right ventricle. The interventricular septum therefore forms the anterior wall and some of the wall on the right side of the left ventricle. The septum is described as having two parts:
+
+
+
+As with the right atrium, the left atrium is derived embryologically from two structures.
+
+■     a muscular part, and ■     a membranous part.
+
+
+
+■     The posterior half, or inflow portion, receives the four pulmonary veins (Fig. 3.73). It has smooth walls and derives from the proximal parts of the pulmonary veins that  are  incorporated  into  the  left  atrium  during development.
+■     The anterior half is continuous with the left auricle. It contains musculi pectinati and derives from the embry-onic primitive atrium. Unlike the crista terminalis in the right atrium, no distinct structure separates the two components of the left atrium.
+
+The interatrial septum is part of the anterior wall of the
+
+
+The muscular part is thick and forms the major part of the septum, whereas the membranous part is the thin, upper part of the septum. A third part of the septum may be considered an atrioventricular part because of its posi-tion above the septal cusp of  the tricuspid valve. This superior location places this part of the septum between the left ventricle and right atrium.
+
+Mitral valve
+The left atrioventricular orifice opens into the posterior right side of  the superior part of  the left ventricle. It is closed during ventricular contraction by the mitral valve
+
+
+
+left atrium. The thin area or depression in the septum is the valve of the foramen ovale and is opposite the floor of the fossa ovalis in the right atrium.
+During development, the valve of the foramen ovale prevents blood from passing from the left atrium to the right atrium. This valve may not be completely fused in some adults, leaving a “probe patent” passage between the right atrium and the left atrium.
+
+(left atrioventricular valve), which is also referred to as the bicuspid valve because it has two cusps, the ante-rior and posterior cusps (Fig. 3.74). The bases of  the cusps  are  secured  to  a  fibrous  ring  surrounding  the opening, and the cusps are continuous with each other at the commissures. The coordinated action of the papil-lary muscles and chordae tendineae is as described for the right ventricle.
+199
+Thorax
+
+
+
+
+
+
+Arch of aorta
+
+
+
+Left auricle
+
+
+Pulmonary arteries
+
+
+
+
+Pulmonary veins
+
+
+
+
+Valve of foramen ovale
+
+Left atrium
+
+Mitral valve
+
+
+
+A
+Left ventricle
+
+
+
+
+
+
+Ascending aorta
+
+
+Right pulmonary vein
+
+Esophagus
+
+
+
+
+
+
+
+
+Right ventricle
+
+
+Left atrium
+Left pulmonary vein
+
+
+
+Thoracic aorta
+
+
+B
+
+Fig. 3.73  Left atrium. A. Internal view. B. Axial computed tomography image showing the pulmonary veins entering the left atrium.
+
+
+
+
+
+
+
+
+200
+Regional Anatomy  •  Mediastinum	3
+
+
+
+
+
+
+
+Arch of aorta
+
+
+
+Mitral valve anterior cusp
+
+
+Pulmonary arteries
+
+Chordae tendineae
+
+
+Pulmonary veins
+
+Anterior papillary muscle
+
+
+
+Trabeculae carneae	Left atrium
+
+
+Coronary sinus
+
+
+Posterior papillary
+muscle	Mitral valve posterior cusp
+
+Fig. 3.74  Internal view of the left ventricle.
+
+
+
+Aortic valve
+The aortic vestibule, or outflow tract of the left ventricle, is continuous superiorly with the ascending aorta. The opening from the left ventricle into the aorta is closed by the aortic valve. This valve is similar in structure to the pulmonary valve. It consists of  three semilunar cusps with the free edge of  each projecting upward into the
+
+
+
+Nodule
+
+
+
+Aortic sinus
+
+lumen of the ascending aorta (Fig. 3.75).
+Between  the  semilunar  cusps  and  the  wall  of  the ascending aorta are pocket-like sinuses—the right, left, and posterior aortic sinuses. The right and left coro-nary  arteries  originate  from  the  right  and  left  aortic sinuses. Because of  this, the posterior aortic sinus and cusp  are  sometimes  referred  to  as  the  noncoronary sinus and cusp.
+The functioning of the aortic valve is similar to that of
+
+
+Opening for right coronary artery
+
+Nodule Aortic sinus   Lunule
+
+
+
+Left coronary artery
+
+
+
+the  pulmonary  valve  with  one  important  additional process: as blood recoils after ventricular contraction and fills the aortic sinuses, it is automatically forced into the
+
+
+Right coronary artery
+
+
+Right   Posterior   Left
+Semilunar cusps
+
+coronary arteries because these vessels originate from the right and left aortic sinuses.
+
+
+Fig. 3.75  Anterior view of the aortic valve.	201
+Thorax
+
+
+
+In the clinic
+
+Valve disease
+Valve problems consist of two basic types:
+
+■     the left fibrous trigone, which is a thickened area of connective tissue between the aortic ring and the left atrioventricular ring (Fig. 3.76).
+
+
+
+■     incompetence (insufficiency), which results from poorly functioning valves; and
+■     stenosis, a narrowing of the orifice, caused by the valve’s inability to open fully.
+
+The cardiac skeleton helps maintain the integrity of the openings it surrounds and provides points of attachment for the cusps. It also separates the atrial musculature from the ventricular musculature. The atrial myocardium origi-
+
+
+
+Mitral valve disease is usually a mixed pattern of stenosis and incompetence, one of which usually predominates. Both stenosis and incompetence lead to a poorly functioning valve and subsequent heart changes, which include:
+
+nates from the upper border of  the rings, whereas the ventricular myocardium originates from the lower border of the rings.
+The cardiac skeleton also serves as a dense connective tissue  partition  that  electrically  isolates  the  atria  from
+
+
+
+■     left ventricular hypertrophy (this is appreciably less marked in patients with mitral stenosis);
+■     increased pulmonary venous pressure; ■     pulmonary edema; and
+■     enlargement (dilation) and hypertrophy of the left atrium.
+
+the ventricles. The atrioventricular bundle, which passes through the anulus, is the single connection between these two groups of myocardium.
+
+
+Coronary vasculature
+
+
+
+Mitral valve stenosis can be congenital or acquired; in the latter, the most common cause is rheumatic fever. Stenosis usually occurs decades after an acute episode of rheumatic endocarditis.
+Aortic valve disease, both aortic stenosis and aortic regurgitation (backflow), can produce marked heart failure. Aortic valve stenosis is the most common type of cardiac valve disease and results from atherosclerosis causing calcification of the valve leaflets. It can also be caused by postinflammatory or postrheumatic conditions. These may lead to aortic regurgitation such as infective endocarditis, degenerative valve disease, rheumatic fever, or trauma.
+Valve disease in the right side of the heart (affecting the tricuspid or pulmonary valve) is most likely caused by infection. Intravenous drug use, alcoholism, indwelling catheters, and extensive burns predispose to infection of the valves, particularly the tricuspid valve. The resulting valve dysfunction produces abnormal pressure changes in the right atrium and right ventricle, and these can induce cardiac failure.
+
+
+Cardiac skeleton
+The cardiac skeleton is a collection of dense, fibrous con-nective tissue in the form of four rings with interconnecting
+
+Two coronary arteries arise from the aortic sinuses in the initial  portion  of  the  ascending  aorta  and  supply  the muscle and other tissues of the heart. They circle the heart in the coronary sulcus, with marginal and interventricular branches, in the interventricular sulci, converging toward the apex of the heart (Fig. 3.77).
+The returning venous blood passes through cardiac veins, most of which empty into the coronary sinus. This large venous structure is located in the coronary sulcus on the posterior surface of the heart between the left atrium and left ventricle. The coronary sinus empties into the right atrium between the opening of the inferior vena cava and the right atrioventricular orifice.
+
+Coronary arteries
+Right coronary artery. The right coronary artery originates from the right aortic sinus of the ascending aorta. It passes anteriorly and then descends vertically in the coronary sulcus, between the right atrium and right ventricle (Fig. 3.78A). On reaching the inferior margin of the heart, it turns posteriorly and continues in the sulcus onto the diaphragmatic surface and base of the heart. During this course, several branches arise from the main stem of the vessel:
+
+
+
+areas in a plane between the atria and the ventricles. The four rings of the cardiac skeleton surround the two atrio-ventricular orifices, the aortic orifice and opening of the pulmonary trunks. They are the anulus fibrosus. The interconnecting areas include:
+
+■     An early atrial branch passes in the groove between the right auricle and ascending aorta, and gives off the sinu-atrial  nodal  branch (Fig. 3.78A), which passes posteriorly around the superior vena cava to supply the sinu-atrial node.
+■     A right marginal branch is given off as the right coro-
+
+
+
+■     the right fibrous trigone, which is a thickened area of connective  tissue  between  the  aortic  ring  and  right
+202	atrioventricular ring; and
+
+nary artery approaches the inferior (acute) margin of the heart (Fig. 3.78A,B) and continues along this border toward the apex of the heart.
+Regional Anatomy  •  Mediastinum	3
+
+
+Anterior
+Fibrous ring of pulmonary valve Ant
+Rt Lt
+
+Left fibrous trigone
+
+Lt	Rt	Fibrous ring of aortic valve
+
+
+
+Left	Post
+Ant	Ant
+
+Left atrioventricular ring	Septal
+
+
+Right
+
+Atrioventricular bundle
+
+
+Post
+
+Post	Right atrioventricular ring
+
+
+
+Right fibrous trigone	Posterior
+
+Fig. 3.76  Cardiac skeleton (atria removed).
+
+
+
+
+■     As the right coronary artery continues on the base/ diaphragmatic surface of the heart, it supplies a small branch  to  the  atrioventricular  node  before  giving off its final major branch, the posterior interventricu-lar branch (Fig. 3.78A), which lies in the posterior interventricular sulcus.
+
+arise and descend diagonally across the anterior surface of the left ventricle.
+■     The circumflex branch (Fig. 3.78A,C) courses toward the left, in the coronary sulcus and onto the base/ diaphragmatic surface of the heart, and usually ends before reaching the posterior interventricular sulcus. A large branch, the left marginal artery (Fig. 3.78A,C),
+
+
+
+The right coronary artery supplies the right atrium and right ventricle, the sinu-atrial and atrioventricular nodes, the interatrial septum, a portion of  the left atrium, the posteroinferior one third of  the interventricular septum, and a portion of the posterior part of the left ventricle.
+Left coronary artery.  The left coronary artery originates from the left aortic sinus of the ascending aorta. It passes between the pulmonary trunk and the left auricle before entering the coronary sulcus. Emerging from behind the pulmonary trunk, the artery divides into its two terminal branches, the anterior interventricular and the circumflex
+
+usually arises from it and continues across the rounded obtuse margin of the heart.
+
+
+The distribution pattern of  the left coronary artery enables it to supply most of the left atrium and left ventricle, and most of  the interventricular septum, including the atrioventricular bundle and its branches.
+Variations  in  the  distribution  patterns  of  coronary  arter-ies.  Several major variations in the basic distribution pat-terns of the coronary arteries occur.
+
+(Fig. 3.78A).                                                                                  ■     The distribution pattern described above for both right and left coronary arteries is the most common and
+
+■     The anterior interventricular branch (left anterior descending artery—LAD) (Fig. 3.78A,C) continues
+
+consists  of  a  right  dominant  coronary  artery.  This means that the posterior interventricular branch arises
+
+around  the  left  side  of  the  pulmonary  trunk  and	from  the  right  coronary  artery. The  right  coronary
+
+descends obliquely toward the apex of the heart in the anterior interventricular sulcus (Fig. 3.78A,C). During its course, one or two large diagonal branches may
+
+artery therefore supplies a large portion of the posterior wall of the left ventricle and the circumflex branch of
+the left coronary artery is relatively small.	203
+Thorax
+
+
+
+
+
+
+
+
+
+
+
+Ascending aorta
+
+
+
+
+
+Marginal branches
+Coronary sulcus
+
+
+Anterior interventricular branches
+
+
+
+Marginal branches
+
+
+
+Apex A	Posterior interventricular
+branches
+
+
+
+
+Anterior
+
+Aortic sinuses
+
+
+
+
+
+
+
+Left	Right
+
+
+
+Coronary sulcus
+
+Right atrioventricular opening
+
+
+
+Coronary sinus
+B	Posterior
+
+204
+Fig. 3.77  Cardiac vasculature. A. Anterior view. B. Superior view (atria removed).
+Regional Anatomy  •  Mediastinum	3
+
+
+
+
+
+
+
+Left coronary artery
+
+
+Sinu-atrial nodal branch of right coronary artery
+
+
+Left auricle
+
+
+Circumflex branch
+of left coronary artery
+
+Right coronary artery
+
+
+
+
+Right atrium
+
+
+Right ventricle
+
+Left marginal branch of circumflex branch
+
+
+Anterior interventricular branch of left
+coronary artery
+
+
+Left ventricle
+
+
+Diagonal branch of
+anterior interventricular branch
+
+
+Right marginal branch of right coronary artery
+
+A
+
+
+Posterior interventricular branch of right coronary artery
+
+
+
+Right coronary artery
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+B
+
+Circumflex branch	Anterior interventricular branch
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+C
+
+
+Posterior interventricular branch	Left marginal branch
+Right marginal branch
+
+Fig. 3.78  A. Anterior view of coronary arterial system. Right dominant coronary artery. B. Left anterior oblique view of right coronary artery.	205 C. Right anterior oblique view of left coronary artery.
+Thorax
+
+
+
+
+
+
+
+Left coronary artery
+
+
+Sinu-atrial nodal branch of left coronary artery
+
+Circumflex branch
+of left coronary artery
+
+
+
+Left marginal branch of circumflex branch
+
+Right coronary artery	Anterior interventricular branch of left coronary artery
+
+
+
+
+
+Diagonal branch of
+anterior interventricular branch
+
+
+Right marginal branch of right coronary artery
+
+
+Posterior interventricular branch of circumflex branch of left coronary artery
+
+
+Fig. 3.79  Left dominant coronary artery.
+
+
+
+
+
+■     In contrast, in hearts with a left dominant coronary artery, the posterior interventricular branch arises from an	enlarged	circumflex	branch	and	supplies most   of   the   posterior   wall   of   the   left   ventricle (Fig. 3.79).
+■     Another point of variation relates to the arterial supply to the sinu-atrial and atrioventricular nodes. In most cases, these two structures are supplied by the right coronary artery. However, vessels from the circumflex branch of the left coronary artery occasionally supply these structures.
+
+
+In the clinic
+
+Clinical terminology for coronary arteries
+In practice, physicians use alternative names for the coronary vessels. The short left coronary artery is referred to as the left main stem vessel. One of its primary branches, the anterior interventricular artery, is termed the left anterior descending artery (LAD). Similarly, the terminal branch of the right coronary artery, the posterior interventricular artery, is termed the posterior descending artery (PDA).
+
+
+
+
+
+
+
+
+
+206
+Regional Anatomy  •  Mediastinum	3
+
+
+
+In the clinic
+
+Heart attack
+A heart attack occurs when the perfusion to the myocardium is insufficient to meet the metabolic needs of the tissue, leading to irreversible tissue damage. The most common cause is a total occlusion of a major coronary artery.
+Coronary artery disease
+Occlusion of a major coronary artery, usually due to atherosclerosis, leads to inadequate oxygenation of an area of myocardium and cell death (Fig. 3.80). The severity of the problem will be related to the size and location of the artery involved, whether or not the blockage is complete, and whether there are collateral vessels to provide perfusion
+to the territory from other vessels. Depending on the severity, patients can develop pain (angina) or a myocardial infarction (MI).
+Percutaneous coronary intervention
+This is a technique in which a long fine tube (a catheter) is inserted into the femoral artery in the thigh and passed through the external and common iliac arteries and into the
+
+
+
+abdominal aorta. It continues to be moved upward through the thoracic aorta to the origins of the coronary arteries. The coronaries may also be approached via the radial or brachial arteries. A fine wire is then passed into the coronary artery and is used to cross the stenosis. A fine balloon is then passed over the wire and may be inflated at the level of the obstruction, thus widening it; this is termed angioplasty. More commonly, this is augmented by placement of a fine wire mesh (a stent) inside the obstruction to hold it open. Other percutaneous interventions are suction extraction of a coronary thrombus and rotary ablation of a plaque.
+Coronary artery bypass grafts
+If coronary artery disease is too extensive to be treated by percutaneous intervention, surgical coronary artery bypass grafting may be necessary. The great saphenous vein, in the lower limb, is harvested and used as a graft. It is divided into several pieces, each of which is used to bypass blocked sections of the coronary arteries. The internal thoracic and radial arteries can also be used.
+
+
+
+
+
+
+
+
+
+Anterior interventricular artery
+
+
+
+
+A	B
+
+
+
+
+
+Anterior interventricular artery
+
+
+
+
+D
+C
+
+
+Fig. 3.80  A and B. Axial maximum intensity projection (MIP) CT image through the heart. A. Normal anterior interventricular (left anterior descending) artery. B. Stenotic (calcified) anterior interventricular (left anterior descending) artery. C and D. Vertical long axis multiplanar reformation (MRP) CT image through the heart. C. Normal anterior interventricular (left anterior descending) artery. D. Stenotic (calcified) anterior interventricular (left anterior descending) artery.
+
+
+
+207
+Thorax
+
+
+
+In the clinic
+
+Classic symptoms of heart attack
+The typical symptoms are chest heaviness or pressure, which can be severe, lasting more than 20 minutes, and often associated with sweating. The pain in the chest (which may be described as an “elephant sitting on my chest” or by using a clenched fist to describe the pain [Levine sign]) often radiates to the arms (left more common than the right), and can be associated with nausea. The severity of ischemia and infarction depends on the rate at which the occlusion or stenosis has occurred and whether or not collateral channels have had a chance to develop.
+
+In the clinic
+
+Are heart attack symptoms the same in men and women?
+Although men and women can experience the typical symptoms of severe chest pain, cold sweats, and pain in the left arm, women are more likely than men to have subtler, less recognizable symptoms. These may include abdominal pain, achiness in the jaw or back, nausea, shortness of breath, or simply fatigue. The mechanism of this difference is not understood, but it is important to consider cardiac ischemia for a wide range of symptoms.
+
+
+
+
+In the clinic
+
+Common congenital heart defects
+The most common abnormalities that occur during development are those produced by a defect in the atrial and ventricular septa.
+A defect in the interatrial septum allows blood to pass from one side of the heart to the other from the chamber with the higher pressure to the chamber with the lower pressure; this is clinically referred to as a shunt. An atrial septal defect (ASD) allows oxygenated blood to flow from the left atrium (higher pressure) across the ASD into the right atrium (lower pressure), resulting in a left to right shunt and volume overload in the right-sided circulation. Many patients with ASD are asymptomatic, but in some cases the ASD may cause symptoms and needs to be closed surgically or by endovascular devices. Occasionally, increased blood flow into the right atrium over many years leads to right atrial and right ventricular hypertrophy and enlargement of the pulmonary trunk, resulting in pulmonary arterial hypertension. In such cases, the patients can present with shortness of breath, increasing tiredness, palpitations, fainting episodes and heart failure. In ASD, the left ventricle is not enlarged as it is not affected by increased returning blood volume.
+The most common of all congenital heart defects are those that occur in the ventricular septum—ventriculoseptal defect (VSD). These lesions are most frequent in the membranous portion of the septum and they allow blood to flow from the left ventricle (higher pressure) to the right ventricle (lower pressure), leading to an abnormal communication between the systemic and pulmonary circulation. This leads to right ventricular hypertrophy, increased pulmonary blood flow, elevated arterial pulmonary pressure, and increased blood volume returning to the left ventricle, causing its dilation. Increased pulmonary pressure in most severe cases may cause pulmonary edema. If large enough and left untreated, VSDs can produce marked clinical problems that might require surgery. VSD may be an isolated abnormality or part of a syndromic constellation, such as the
+208	tetralogy of Fallot.
+
+
+
+The tetralogy of Fallot, the most common cyanotic congenital heart disorder diagnosed soon after birth, classically consists of four abnormalities: pulmonary stenosis, VSD, overriding aorta (originating to a varying degree from the right ventricle), and right ventricular hypertrophy. The underdevelopment of the right ventricle and pulmonary stenosis reduce blood flow to the lungs, leading to reduced volume of oxygenated blood returning to the heart. The defect in the interventricular septum causes mixing of oxygenated and nonoxygenated blood. The mixed blood is then delivered by the aorta to the major organs, resulting in poor oxygenation and cyanosis. Infants can present with cyanosis at birth or develop episodes of cyanosis while feeding or crying (tet spells). Most affected infants require surgical intervention. The advent of cardiopulmonary bypass was crucial in delivering highly satisfactory surgical results.
+Occasionally, the ductus arteriosus, which connects the left branch of the pulmonary artery to the inferior aspect of the aortic arch, fails to close at birth. This is termed a patent or persistent ductus arteriosus (PDA). When this occurs, the oxygenated blood in the aortic arch (higher pressure) passes into the left branch of the pulmonary artery (lower pressure) and produces pulmonary hypertension and left atrial and ventricular enlargement. The prognosis in patients with isolated PDA is extremely good, as most do not have any major sequelae after surgical closure.
+All of these defects produce a left-to-right shunt, indicating that oxygenated blood from the left side of the heart is being mixed with deoxygenated blood from the right side of the heart before being recirculated into the pulmonary circulation. These shunts are normally compatible with life, but surgery or endovascular treatment may be necessary.
+Rarely, a shunt is right-to-left. In isolation, this is fatal; however, this type of shunt is often associated with other anomalies, so some deoxygenated blood is returned to the lungs and the systemic circulation.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+In the clinic
+
+Cardiac auscultation
+Auscultation of the heart reveals the normal audible cardiac cycle, which allows the clinician to assess heart rate, rhythm, and regularity. Furthermore, cardiac murmurs that have characteristic sounds within the phases of the cardiac cycle can be demonstrated (Fig. 3.81).
+
+the great cardiac vein gradually enlarges to form the coro-nary sinus, which enters the right atrium (Fig. 3.82B).
+Middle cardiac vein.  The middle cardiac vein (posterior interventricular vein) begins near the apex of  the heart and ascends in the posterior interventricular sulcus toward the coronary sinus (Fig. 3.82B). It is associated with the posterior interventricular branch of the right or left coro-nary artery throughout its course.
+Small cardiac vein.  The small cardiac vein begins in the
+
+
+
+Closure of mitral and tricuspid valves
+
+
+Closure of aortic and pulmonary valves
+
+
+
+
+
+
+
+
+
+Atrial contraction
+
+lower anterior section of the coronary sulcus between the right atrium and right ventricle (Fig. 3.82A). It continues in this groove onto the base/diaphragmatic surface of the heart where it enters the coronary sinus at its atrial end. It is a companion of the right coronary artery throughout its course and may receive the right marginal vein (Fig. 3.82A). This small vein accompanies the marginal branch of the right coronary artery along the acute margin of the heart. If the right marginal vein does not join the small cardiac vein, it enters the right atrium directly.
+Posterior cardiac vein.  The posterior cardiac vein lies on
+
+
+
+Ventricular pressure
+R
+P	T
+ECG
+Q S
+
+the posterior surface of the left ventricle just to the left of the middle cardiac vein (Fig. 3.82B). It either enters the coronary sinus directly or joins the great cardiac vein.
+Other  cardiac  veins.  Two additional groups of  cardiac veins  are  also  involved  in  the  venous  drainage  of  the heart.
+
+
+
+1st	2nd
+Heart
+sounds	"lub"	"dub"
+SYSTOLE	DIASTOLE
+
+1st
+
+"lub"
+SYSTOLE
+
+
+■     The anterior veins of the right ventricle (anterior cardiac veins) are small veins that arise on the anterior surface of the right ventricle (Fig. 3.82A). They cross the coronary sulcus and enter the anterior wall of the
+
+
+
+Fig. 3.81  Heart sounds and how they relate to valve closure, the electrocardiogram (ECG), and ventricular pressure.
+
+right atrium. They drain the anterior portion of  the right ventricle. The right marginal vein may be part of  this group if  it does not enter the small cardiac vein.
+
+■     A  group  of   smallest  cardiac  veins  (venae  cordis minimae  or  veins  of  Thebesius)  have  also  been
+
+
+Cardiac veins
+The coronary sinus receives four major tributaries: the great, middle, small, and posterior cardiac veins.
+Great  cardiac  vein.  The  great  cardiac  vein  begins  at the apex of the heart (Fig. 3.82A). It ascends in the anterior interventricular sulcus, where it is related to the anterior interventricular artery and is often termed the anterior interventricular vein. Reaching the coronary sulcus, the
+
+described. Draining directly into the cardiac chambers, they are numerous in the right atrium and right ven-tricle, are occasionally associated with the left atrium, and are rarely associated with the left ventricle.
+
+Coronary lymphatics
+The lymphatic vessels of  the heart follow the coronary arteries and drain mainly into:
+
+
+
+great cardiac vein turns to the left and continues onto the base/diaphragmatic surface of the heart. At this point, it is
+
+■     brachiocephalic nodes, anterior to the brachiocephalic veins; and
+
+
+
+associated with the circumflex branch of the left coronary artery. Continuing along its path in the coronary sulcus,
+
+■     tracheobronchial  nodes,  at  the  inferior  end  of  the trachea.
+
+
+209
+Thorax
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Great cardiac vein
+
+
+Anterior veins of right ventricle
+
+Coronary sinus
+Anterior interventricular vein
+
+
+
+Small cardiac vein
+
+
+
+A	Right marginal vein	Middle cardiac vein
+
+
+
+
+
+
+
+
+
+
+Great cardiac vein
+
+
+
+
+Posterior cardiac vein
+
+
+Small cardiac vein
+
+
+Coronary sinus
+
+
+
+Middle cardiac vein B
+
+Fig. 3.82  Major cardiac veins. A. Anterior view of major cardiac veins. B. Posteroinferior view of major cardiac veins.
+
+210
+Regional Anatomy  •  Mediastinum	3
+
+
+
+
+Cardiac conduction system
+The musculature of the atria and ventricles is capable of contracting spontaneously. The cardiac conduction system initiates  and  coordinates  contraction.  The  conduction system  consists  of  nodes  and  networks  of  specialized cardiac muscle cells organized into four basic components:
+
+The excitation signals generated by the sinu-atrial node spread across the atria, causing the muscle to contract.
+
+Atrioventricular node
+Concurrently, the wave of excitation in the atria stimulates the atrioventricular node, which is located near the opening of the coronary sinus, close to the attachment of
+
+
+
+
+■     the sinu-atrial node,
+■     the atrioventricular node,
+■     the atrioventricular bundle with its right and left bundle branches, and
+■     the  subendocardial  plexus  of  conduction  cells  (the Purkinje fibers).
+
+The unique distribution pattern of the cardiac conduc-
+
+the septal cusp of the tricuspid valve, and within the atrio-ventricular septum (Fig. 3.83A).
+The atrioventricular node is a collection of specialized cells that forms the beginning of an elaborate system of conducting  tissue,  the  atrioventricular  bundle,  which extends   the   excitatory   impulse   to   all   ventricular musculature.
+
+Atrioventricular bundle
+
+tion   system   establishes   an   important   unidirectional       The atrioventricular bundle is a direct continuation pathway of excitation/contraction. Throughout its course,       of   the  atrioventricular  node  (Fig.  3.83A).  It  follows
+
+large branches of  the conduction system are insulated from the surrounding myocardium by connective tissue. This tends to decrease inappropriate stimulation and con-traction of cardiac muscle fibers.
+The number of  functional contacts between the con-duction pathway and cardiac musculature greatly increases in the subendocardial network.
+Thus, a unidirectional wave of excitation and contrac-tion is established, which moves from the papillary muscles and apex of the ventricles to the arterial outflow tracts.
+
+In the clinic
+
+Cardiac conduction system
+The cardiac conduction system can be affected by coronary artery disease. The normal rhythm may be disturbed if the blood supply to the coronary conduction system is disrupted. If a dysrhythmia affects the heart rate or the order in which the chambers contract, heart failure and death may ensue.
+
+
+Sinu-atrial node
+Impulses  begin  at  the  sinu-atrial  node,  the  cardiac pacemaker. This collection of cells is located at the supe-rior end of  the crista terminalis at the junction of  the superior vena cava and the right atrium (Fig. 3.83A).
+
+along the lower border of  the membranous part of  the interventricular septum before splitting into right and left bundles.
+The right bundle branch continues on the right side of the interventricular septum toward the apex of the right ventricle. From the septum it enters the septomarginal trabecula to reach the base of the anterior papillary muscle. At this point, it divides and is continuous with the final component of the cardiac conduction system, the suben-docardial plexus of ventricular conduction cells or Purkinje fibers. This network of specialized cells spreads throughout the ventricle to supply the ventricular musculature, includ-ing the papillary muscles.
+The left bundle branch passes to the left side of the muscular  interventricular  septum  and  descends  to  the apex of  the left ventricle (Fig. 3.83B). Along its course it gives off branches that eventually become continuous with the subendocardial plexus of  conduction cells (Purkinje fibers). As with the right side, this network of specialized cells spreads the excitation impulses through-out the left ventricle.
+
+Cardiac innervation
+The autonomic division of the peripheral nervous system is directly responsible for regulating:
+
+
+
+This is also the junction between the parts of  the right atrium derived from the embryonic sinus venosus and the atrium proper.
+
+■     heart rate,
+■     force of each contraction, and ■     cardiac output.
+
+
+
+
+
+211
+Thorax
+
+
+
+
+Aorta
+
+
+Pulmonary trunk
+
+
+Superior vena cava
+
+
+
+Sinu-atrial node
+Right bundle branch
+
+
+
+Atrioventricular bundle
+
+Atrioventricular node
+
+
+
+
+Inferior vena cava	Septomarginal trabecula
+
+Right ventricle A
+Anterior papillary muscle
+
+
+Aorta
+
+Pulmonary trunk
+
+
+Left bundle branch
+
+
+
+
+
+Anterior papillary muscle
+
+
+Right pulmonary veins
+
+
+
+
+Left atrium
+
+Posterior papillary muscle
+
+
+B	Left ventricle
+
+Fig. 3.83  Conduction system of the heart. A. Right chambers. B. Left chambers.
+
+
+212
+Regional Anatomy  •  Mediastinum	3
+
+
+
+Branches from both the parasympathetic and sympa-thetic systems contribute to the formation of the cardiac plexus. This plexus consists of a superficial part, inferior to the aortic arch and between it and the pulmonary trunk (Fig. 3.84A), and a deep part, between the aortic arch and the tracheal bifurcation (Fig. 3.84B).
+
+From  the  cardiac  plexus,  small  branches  that  are mixed nerves containing both sympathetic and parasym-pathetic fibers supply the heart. These branches affect nodal  tissue  and  other  components  of  the  conduction system, coronary blood vessels, and atrial and ventricular musculature.
+
+
+
+
+Cardiac nerves from sympathetic trunk
+
+
+
+
+
+
+
+Right vagus nerve
+
+
+Vagal cardiac branches
+
+
+Arch of aorta
+
+Left vagus nerve
+
+
+
+Vagal cardiac branches
+
+Superficial cardiac plexus
+
+
+Superior vena cava
+Pulmonary trunk
+
+
+
+
+
+A
+Cardiac nerves from sympathetic trunk
+
+
+
+
+
+
+Right recurrent laryngeal nerve
+Left recurrent laryngeal nerve Right vagus nerve
+Left vagus nerve
+
+Vagal cardiac branches
+
+Vagal cardiac branches
+
+Deep cardiac plexus
+
+
+
+
+
+B
+
+Fig. 3.84  Cardiac plexus. A. Superficial. B. Deep.	213
+Thorax
+
+
+
+
+Parasympathetic innervation
+Stimulation of the parasympathetic system:
+
+Visceral afferents
+Visceral afferents from the heart are also a component of
+
+
+
+
+■     decreases heart rate,
+■     reduces force of contraction, and ■     constricts the coronary arteries.
+
+The  preganglionic  parasympathetic  fibers  reach  the
+
+the cardiac plexus. These fibers pass through the cardiac plexus and return to the central nervous system in the cardiac nerves from the sympathetic trunk and in the vagal cardiac branches.
+The afferents associated with the vagal cardiac nerves return to the vagus nerve [X]. They sense alterations in
+
+
+
+heart as cardiac branches from the right and left vagus nerves. They  enter  the  cardiac  plexus  and  synapse  in ganglia located either within the plexus or in the walls of the atria.
+
+Sympathetic innervation
+Stimulation of the sympathetic system:
+
+blood pressure and blood chemistry and are therefore pri-marily concerned with cardiac reflexes.
+The afferents associated with the cardiac nerves from the sympathetic trunks return to either the cervical or the thoracic portions of the sympathetic trunk. If they are in the cervical portion of the trunk, they normally descend to the thoracic region, where they reenter the upper four or
+
+
+
+
+■     increases heart rate, and
+■     increases the force of contraction.
+
+Sympathetic fibers reach the cardiac plexus through the
+
+five thoracic spinal cord segments, along with the afferents from the thoracic region of the sympathetic trunk. Visceral afferents associated with the sympathetic system conduct pain sensation from the heart, which is detected at the cellular  level  as  tissue-damaging  events  (i.e.,  cardiac
+
+
+
+cardiac nerves from the sympathetic trunk. Preganglionic sympathetic fibers from the upper four or five segments of  the thoracic spinal cord enter and move through the sympathetic trunk. They synapse in cervical and upper thoracic sympathetic ganglia, and postganglionic fibers proceed as bilateral branches from the sympathetic trunk to the cardiac plexus.
+
+ischemia).  This  pain  is  often  “referred”  to  cutaneous regions supplied by the same spinal cord levels (see “In the clinic: Referred pain.” p. 46, and “Case 1,” pp. 244–246).
+
+Pulmonary trunk
+The pulmonary trunk is contained within the pericardial sac (Fig. 3.85), is covered by the visceral layer of serous
+
+
+
+
+
+
+
+
+
+
+Ascending aorta
+Superior vena cava
+
+Pulmonary trunk	Arch of aorta
+
+Left pulmonary artery
+
+
+Superior vena cava
+
+Right pulmonary artery
+
+
+
+Left pulmonary veins
+
+
+Right pulmonary veins
+
+
+Right atrium
+
+Inferior vena cava
+
+
+A	B	Oblique pericardial sinus
+
+Fig. 3.85  Major vessels within the middle mediastinum. A. Anterior view. B. Posterior view. 214
+Regional Anatomy  •  Mediastinum	3
+
+
+
+pericardium, and is associated with the ascending aorta in a common sheath. It arises from the conus arteriosus of the right ventricle at the opening of the pulmonary trunk slightly anterior to the aortic orifice and ascends, moving posteriorly and to the left, lying initially anterior and then to the left of  the ascending aorta. At approximately the level of the intervertebral disc between vertebrae TV and TVI, opposite the left border of the sternum and posterior to the third left costal cartilage, the pulmonary trunk divides into:
+
+within the pericardial sac before entering the right atrium. While within the pericardial sac, it is covered by serous pericardium except for a small portion of  its posterior surface (Fig. 3.85B).
+A very short segment of each of the pulmonary veins is also within the pericardial sac. These veins, usually two from each lung, pass through the fibrous pericardium and enter the superior region of the left atrium on its posterior surface. In the pericardial sac, all but a portion of  the posterior surface of these veins is covered by serous peri-
+
+
+
+
+■     the right pulmonary artery, which passes to the right, posterior to the ascending aorta and the superior vena cava, to enter the right lung; and
+■     the left pulmonary artery, which passes inferiorly to the arch of the aorta and anteriorly to the descending aorta to enter the left lung.
+
+cardium. In addition, the oblique pericardial sinus is between the right and left pulmonary veins, within the pericardial sac (Fig. 3.85B).
+
+
+Superior mediastinum
+The superior mediastinum is posterior to the manu-brium of the sternum and anterior to the bodies of the first
+
+Ascending aorta	four thoracic vertebrae (see Fig. 3.57).
+
+The ascending aorta is contained within the pericardial sac and is covered by a visceral layer of serous pericardium, which also surrounds the pulmonary trunk in a common sheath (Fig. 3.85A).
+The origin of the ascending aorta is the aortic orifice at the base of the left ventricle, which is level with the lower edge of the third left costal cartilage, posterior to the left half  of  the sternum. Moving superiorly, slightly forward and to the right, the ascending aorta continues to the level of the second right costal cartilage. At this point, it enters
+
+■     Its superior boundary is an oblique plane passing from the jugular notch upward and posteriorly to the superior border of vertebra TI.
+■     Inferiorly, a transverse plane passing from the sternal angle to the intervertebral disc between vertebra TIV/V separates it from the inferior mediastinum.
+■     Laterally, it is bordered by the mediastinal part of the parietal pleura on either side.
+
+The superior mediastinum is continuous with the neck
+
+the superior mediastinum and is then referred to as the arch of the aorta.
+Immediately superior to the point where the ascending
+
+above and with the inferior mediastinum below.
+The major structures found in the superior mediastinum (Figs. 3.86 and 3.87) include the:
+
+
+
+aorta arises from the left ventricle are three small outward bulges opposite the semilunar cusps of  the aortic valve. These are the posterior, right, and left aortic sinuses. The right and left coronary arteries originate from the right and left aortic sinuses, respectively.
+
+Other vasculature
+The inferior half  of  the superior vena cava is located within the pericardial sac (Fig. 3.85B). It passes through the  fibrous  pericardium  at  approximately  the  level  of the second costal cartilage and enters the right atrium at  the  lower  level  of   the  third  costal  cartilage.  The portion within the pericardial sac is covered with serous pericardium  except  for  a  small  area  on  its  posterior
+
+
+■     thymus,
+■     right and left brachiocephalic veins, ■     left superior intercostal vein,
+■     superior vena cava,
+■     arch of the aorta with its three large branches, ■     trachea,
+■     esophagus,
+■     phrenic nerves, ■     vagus nerves,
+■     left recurrent laryngeal branch of the left vagus nerve, ■     thoracic duct, and
+■     other small nerves, blood vessels, and lymphatics.
+
+
+
+surface.
+After passing through the diaphragm, at approximately the level of vertebra TVIII, the inferior vena cava enters the fibrous pericardium. A short portion of this vessel is
+
+
+Thymus
+The thymus is the most anterior component of the supe-rior  mediastinum,  lying  immediately  posterior  to  the
+215
+Thorax
+
+
+
+
+
+Right common carotid artery
+
+Right internal jugular vein
+
+Right subclavian artery
+
+Right subclavian vein
+
+
+
+
+
+
+
+
+
+
+
+Right brachiocephalic vein
+Right pulmonary artery
+
+Superior vena cava
+
+
+
+
+Right main bronchus
+
+Trachea
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Esophagus
+
+
+Esophagus
+
+Left common carotid artery
+
+Left internal jugular vein
+
+Left subclavian artery
+Left subclavian vein
+
+
+
+
+
+
+
+
+
+
+
+Left brachiocephalic vein Arch of aorta
+Left pulmonary artery
+
+Left main bronchus
+
+Pulmonary trunk
+Thoracic aorta
+
+Ascending aorta
+
+
+Fig. 3.86  Structures in the superior mediastinum.
+
+
+
+Brachiocephalic trunk	Brachiocephalic trunk
+
+Thymus Right brachiocephalic vein
+Right phrenic nerve
+
+Manubrium of sternum	Right brachiocephalic vein	Left brachiocephalic vein Left brachiocephalic vein
+Left phrenic nerve
+
+
+
+Left common carotid artery
+
+
+Trachea	Left vagus nerve
+
+Left subclavian artery
+
+
+
+
+
+TIII
+Right vagus nerve
+
+Left recurrent laryngeal nerve
+
+
+B
+
+Trachea	Left subclavian artery
+
+A	Esophagus	Thoracic duct	Esophagus	Left common carotid artery
+
+216	Fig. 3.87  Cross section through the superior mediastinum at the level of vertebra TIII. A. Diagram. B. Axial computed tomography image.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+manubrium of the sternum. It is an asymmetrical, bilobed structure (see Fig. 3.58).
+The upper extent of  the thymus can reach into the neck  as  high  as  the  thyroid  gland;  a  lower  portion typically extends into the anterior mediastinum over the pericardial sac.
+
+
+Right and left brachiocephalic veins
+The left and right brachiocephalic veins are located imme-diately posterior to the thymus. They form on each side at the junction between the internal jugular and subclavian veins (see Fig. 3.86). The left brachiocephalic vein crosses
+
+Involved  in  the  early  development  of  the  immune	the midline and joins with the right brachiocephalic vein system, the thymus is a large structure in the child, begins	to form the superior vena cava (Fig. 3.88).
+to atrophy after puberty, and shows considerable size varia-
+
+tion in the adult. In the elderly adult, it is barely identifiable as an organ, consisting mostly of fatty tissue that is some-times arranged as two lobulated fatty structures.
+Arteries to the thymus consist of small branches origi-nating from the internal thoracic arteries. Venous drainage is usually into the left brachiocephalic vein and possibly into the internal thoracic veins.
+Lymphatic drainage returns to multiple groups of nodes at one or more of the following locations:
+
+■     The right brachiocephalic vein begins posterior to the medial end of the right clavicle and passes vertically downward, forming the superior vena cava when it is joined by the left brachiocephalic vein. Venous tributar-ies include the vertebral, first posterior intercostal, and internal thoracic veins. The inferior thyroid and thymic veins may also drain into it.
+■     The left brachiocephalic vein begins posterior to the medial end of  the left clavicle. It crosses to the right,
+
+
+
+
+■     along the internal thoracic arteries (parasternal); ■     at the tracheal bifurcation (tracheobronchial); and ■     in the root of the neck.
+
+moving in a slightly inferior direction, and joins with the right brachiocephalic vein to form the superior vena cava posterior to the lower edge of the right first costal cartilage close to the right sternal border. Venous tribu-taries include the vertebral, first posterior intercostal,
+
+
+
+In the clinic
+
+Ectopic parathyroid glands in the thymus
+The parathyroid glands develop from the third pharyngeal pouch, which also forms the thymus. The thymus is therefore a common site for ectopic parathyroid glands and, potentially, ectopic parathyroid hormone production.
+
+left superior intercostal, inferior thyroid, and internal thoracic veins. It may also receive thymic and pericar-dial  veins. The  left  brachiocephalic  vein  crosses  the midline posterior to the manubrium in the adult. In infants and children the left brachiocephalic vein rises above the superior border of the manubrium and there-fore is less protected.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+217
+Thorax
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Left common carotid artery
+
+
+
+
+Right vagus nerve
+
+Right brachiocephalic vein	Left brachiocephalic vein
+
+Left vagus nerve
+
+
+Azygos vein	Left pulmonary artery Superior vena cava
+
+Left pulmonary veins
+
+
+
+
+
+
+
+
+
+
+
+Fig. 3.88  Superior mediastinum with thymus removed.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+218
+Regional Anatomy  •  Mediastinum	3
+
+
+Left superior intercostal vein
+The left superior intercostal vein receives the second, third,  and  sometimes  the  fourth  posterior  intercostal veins, usually the left bronchial veins, and sometimes the left pericardiacophrenic vein. It passes over the left side
+
+
+
+
+
+
+
+
+Esophagus
+
+
+of  the aortic arch, lateral to the left vagus nerve and medial to the left phrenic nerve, before entering the left brachiocephalic vein (Fig. 3.89). Inferiorly, it may connect with the accessory hemiazygos vein (superior hemia-zygos vein).
+
+
+
+
+
+
+
+
+Rib I
+
+
+
+Left subclavian artery
+
+
+Left brachiocephalic vein
+
+Left phrenic nerve	Left superior intercostal vein
+
+Left vagus nerve
+
+Accessory hemiazygos vein
+
+
+
+Thoracic aorta
+
+
+
+
+
+
+
+Diaphragm
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 3.89  Left superior intercostal vein.
+
+
+
+219
+Thorax
+
+
+
+Superior vena cava
+The vertically oriented superior vena cava begins posterior to the lower edge of the right first costal cartilage, where the right and left brachiocephalic veins join, and terminates at the lower edge of the right third costal cartilage, where it joins the right atrium (see Fig. 3.86).
+The lower half of the superior vena cava is within the pericardial sac and is therefore contained in the middle mediastinum.
+The superior vena cava receives the azygos vein imme-diately before entering the pericardial sac and may also receive pericardial and mediastinal veins.
+The superior vena cava can be easily visualized forming part of the right superolateral border of the mediastinum on a chest radiograph (see Fig. 3.67A).
+
+
+In the clinic
+
+Venous access for central and dialysis lines
+Large systemic veins are used to establish central venous access for administering large amounts of fluid, drugs, and blood. Most of these lines (small-bore tubes) are introduced through venous puncture into the axillary, subclavian, or internal jugular veins. The lines are then passed through the main veins of the superior mediastinum, with the tips of the lines usually residing in the distal portion of the superior vena cava or in the right atrium.
+Similar devices, such as dialysis lines, are inserted into patients who have renal failure, so that a large volume of blood can be aspirated through one channel and reinfused through a second channel.
+
+In the clinic
+
+Using the superior vena cava to access the inferior vena cava
+Because the superior and inferior venae cavae are oriented along the same vertical axis, a guidewire, catheter, or line can be passed from the superior vena cava through the right atrium and into the inferior vena cava. This is a common route of access for such procedures as:
+
+■     transjugular liver biopsy,
+■     transjugular intrahepatic portosystemic shunts (TIPS), and
+■     insertion of an inferior vena cava filter to catch emboli dislodged from veins in the lower limb and pelvis (i.e., patients with deep vein thrombosis [DVT]).
+
+
+
+
+Arch of aorta and its branches
+The thoracic portion of  the aorta can be divided into ascending  aorta,  arch  of  the  aorta,  and  thoracic (descending) aorta. Only the arch of the aorta is in the superior mediastinum. It begins when the ascending aorta emerges from the pericardial sac and courses upward, backward, and to the left as it passes through the superior mediastinum, ending on the left side at vertebral level TIV/V (see Fig. 3.86). Extending as high as the midlevel of the manubrium of the sternum, the arch is initially ante-rior and finally lateral to the trachea.
+Three branches arise from the superior border of  the arch of  the aorta; at their origins, all three are crossed anteriorly by the left brachiocephalic vein.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+220
+Regional Anatomy  •  Mediastinum	3
+
+
+The first branch
+Beginning on the right, the first branch of the arch of the aorta is the brachiocephalic trunk (Fig. 3.90). It is the largest of  the three branches and, at its point of  origin behind the manubrium of the sternum, is slightly anterior to the other two branches. It ascends slightly posteriorly and to the right. At the level of the upper edge of the right sternoclavicular joint, the brachiocephalic trunk divides into:
+
+
+brachiocephalic trunk and ascends through the superior mediastinum along the left side of the trachea.
+The left common carotid artery supplies the left side of the head and neck.
+
+The third branch
+The third branch of the arch of the aorta is the left sub-clavian artery (Fig. 3.90). It arises from the arch of the aorta immediately to the left of, and slightly posterior to,
+
+
+
+
+■     the right common carotid artery, and
+■     the right subclavian artery (see Fig. 3.86).
+
+the left common carotid artery and ascends through the superior mediastinum along the left side of the trachea.
+The left subclavian artery is the major blood supply to the left upper limb.
+
+
+
+The arteries mainly supply the right side of the head and neck and the right upper limb, respectively.
+Occasionally,  the  brachiocephalic  trunk  has  a  small branch, the thyroid ima artery, which contributes to the vascular supply of the thyroid gland.
+
+The second branch
+The second branch of  the arch of  the aorta is the left common carotid artery (Fig. 3.90). It arises from the arch immediately to the left and slightly posterior to the
+
+
+
+Right recurrent laryngeal nerve
+
+Right common carotid artery
+
+
+Ligamentum arteriosum
+The  ligamentum  arteriosum  is  also  in  the  superior mediastinum and is important in embryonic circulation, when it is a patent vessel (the ductus arteriosus). It con-nects the pulmonary trunk with the arch of the aorta and allows  blood  to  bypass  the  lungs  during  development (Fig. 3.90). The vessel closes soon after birth and forms the ligamentous connection observed in the adult.
+
+
+Trachea
+Left recurrent laryngeal nerve
+
+Left common carotid artery
+
+Left subclavian artery
+
+
+Right subclavian artery
+
+
+Brachiocephalic trunk
+
+Right vagus nerve
+
+
+Superior vena cava
+
+
+Ascending aorta
+Right pulmonary artery
+
+
+Left vagus nerve
+
+
+Ligamentum arteriosum
+
+
+
+Left pulmonary artery
+
+
+Left pulmonary veins
+
+Right pulmonary veins
+
+
+
+
+
+
+
+
+
+221
+Fig. 3.90  Superior mediastinum with thymus and venous channels removed.
+Thorax
+
+
+
+In the clinic
+
+Coarctation of the aorta
+Coarctation of the aorta is a congenital abnormality in which the aortic lumen is constricted just distal to the origin of the left subclavian artery. At this point, the aorta becomes significantly narrowed and the blood supply to the lower limbs and abdomen is diminished. Over time, collateral vessels develop around the chest wall and abdomen to supply the lower body. Dilated and tortuous intercostal
+
+
+In the clinic
+
+Thoracic aorta
+Diffuse atherosclerosis of the thoracic aorta may occur in patients with vascular disease, but this rarely produces symptoms. There are, however, two clinical situations in which aortic pathology can produce life-threatening situations.
+
+
+
+vessels, which form a bypass to supply the descending thoracic aorta, may lead to erosions of the inferior margins of the ribs. This can be appreciated on chest radiographs as inferior rib notching and is usually seen in long standing cases. The coarctation also affects the heart, which has to pump the blood at higher pressure to maintain peripheral perfusion. This in turn may produce cardiac failure.
+
+
+
+
+
+it occurs in the ascending aorta or arch of the aorta, blood flow in the coronary and cerebral arteries may be disrupted, resulting in myocardial infarction or stroke. In the abdomen the visceral vessels may be disrupted, producing ischemia to the gut or kidneys.
+
+
+
+Trauma
+The aorta has three fixed points of attachment:
+
+Trachea
+Right lung
+
+Dissection flap
+Left lung
+
+
+■     the aortic valve,
+■     the ligamentum arteriosum, and
+■     the point of passing behind the median arcuate ligament of the diaphragm to enter the abdomen.
+
+
+The rest of the aorta is relatively free from attachment to other structures of the mediastinum. A serious deceleration injury (e.g., in a road traffic accident) is most likely to cause aortic trauma at these fixed points.
+Aortic dissection
+In certain conditions, such as in severe arteriovascular disease, the wall of the aorta can split longitudinally, creating a false channel, which may or may not rejoin into the true lumen distally (Fig. 3.91). This aortic dissection occurs between the intima and media anywhere along its length. If
+
+
+In the clinic
+
+Aortic arch and its anomalies
+The normal aortic arch courses to the left of the trachea and passes over the left main bronchus. A right-sided aortic arch occurs when the vessel courses to the right of the trachea and passes over the right main bronchus. A right-sided arch of aorta is rare and may be asymptomatic. It can be associated with dextrocardia (right-sided heart) and, in some instances, with complete situs inversus
+(left-to-right inversion of the body’s organs). It can also be associated with abnormal branching of the great vessels, particularly with an aberrant left subclavian artery.
+
+
+222
+
+
+
+
+
+
+
+
+Aortic arch—true lumen	Aortic arch—false lumen
+
+Fig. 3.91  Axial CT showing aortic dissection.
+
+
+
+In the clinic
+
+Abnormal origin of great vessels
+Great vessels occasionally have an abnormal origin, including:
+
+■     a common origin of the brachiocephalic trunk and the left common carotid artery,
+■     the left vertebral artery originating from the aortic arch, and
+■     the right subclavian artery originating from the distal portion of the aortic arch and passing behind the esophagus to supply the right arm—as a result, the great vessels form a vascular ring around the trachea and the esophagus, which can potentially produce difficulty swallowing. This configuration is one of the most common aortic arch abnormalities.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+
+Trachea and esophagus
+The trachea is a midline structure that is palpable in the jugular  notch  as  it  enters  the  superior  mediastinum. Posterior  to  it  is  the  esophagus,  which  is  immediately anterior to the vertebral column (Fig. 3.92, and see Figs. 3.86 and 3.87). Significant mobility exists in the vertical positioning of these structures as they pass through the superior mediastinum. Swallowing and breathing cause positional shifts, as may disease and the use of specialized instrumentation.
+As the trachea and esophagus pass through the superior mediastinum, they are crossed laterally by the azygos vein on the right side and the arch of the aorta on the left side.
+
+The trachea divides into the right and left main bronchi at, or just inferior to, the transverse plane between the sternal angle and vertebral level TIV/V (Fig. 3.93), whereas the esophagus continues into the posterior mediastinum.
+
+
+Nerves of the superior mediastinum Vagus nerves
+The vagus  nerves [X] pass through the superior and posterior divisions of  the mediastinum on their way to the abdominal cavity. As they pass through the thorax, they provide parasympathetic innervation to the thoracic viscera  and  carry  visceral  afferents  from  the  thoracic viscera.
+
+
+Thymus
+Superior vena cava	Manubrium of sternum	Superior vena cava	Arch of aorta
+
+
+
+
+Right phrenic nerve
+
+
+Arch of azygos vein
+
+Right vagus nerve
+
+Arch of aorta
+
+
+Left phrenic nerve
+
+Left vagus nerve
+
+Arch of azygos vein
+
+
+
+TIV
+Trachea	Thoracic duct	B
+
+Esophagus
+A
+
+Left recurrent
+laryngeal nerve	Trachea	Esophagus
+
+
+Fig. 3.92  Cross section through the superior mediastinum at the level of vertebra TIV. A. Diagram. B. Axial computed tomography image.
+
+
+Trachea
+
+
+
+
+
+
+Brachiocephalic trunk
+Superior vena cava
+TIV/V vertebral level
+
+
+
+
+Right main bronchus
+
+Fig. 3.93  Trachea in the superior mediastinum.
+
+
+Left brachiocephalic vein
+Arch of aorta
+
+
+
+Left main bronchus
+
+
+Pulmonary trunk
+223
+Thorax
+
+
+
+Visceral afferents in the vagus nerves relay information to the central nervous system about normal physiological processes and reflex activities. They do not transmit pain sensation.
+
+Right vagus nerve
+The right vagus nerve enters the superior mediastinum and lies between the right brachiocephalic vein and the
+
+brachiocephalic trunk. It descends in a posterior direction toward the trachea (Fig. 3.94), crosses the lateral surface of  the trachea, and passes posteriorly to the root of  the right lung to reach the esophagus. Just before the esopha-gus, it is crossed by the arch of the azygos vein.
+As the right vagus nerve passes through the superior mediastinum, it gives branches to the esophagus, cardiac plexus, and pulmonary plexus.
+
+
+
+
+
+
+
+
+Esophagus
+Brachiocephalic trunk
+
+Right brachiocephalic vein
+
+
+
+Trachea
+
+Right vagus nerve
+
+
+Azygos vein
+
+Bronchus
+
+
+Left brachiocephalic vein
+
+Superior vena cava
+
+
+Right phrenic nerve
+
+
+
+Esophagus
+
+Esophageal plexus
+
+
+
+
+
+
+
+Diaphragm
+
+
+
+
+
+
+
+
+Fig. 3.94  Right vagus nerve passing through the superior mediastinum.
+
+
+
+
+
+
+
+224
+Regional Anatomy  •  Mediastinum	3
+
+
+Left vagus nerve
+The left vagus nerve enters the superior mediastinum posterior to the left brachiocephalic vein and between the left common carotid and left subclavian arteries (Fig. 3.95). As it passes into the superior mediastinum, it lies just deep to the mediastinal part of the parietal pleura and crosses the left side of the arch of the aorta. It continues to descend in a posterior direction and passes posterior to the root of the  left  lung  to  reach  the  esophagus  in  the  posterior mediastinum.
+
+
+
+
+Rib I Left common carotid artery
+Brachiocephalic trunk
+
+Left brachiocephalic vein
+
+
+As the left vagus nerve passes through the superior mediastinum,  it  gives  branches  to  the  esophagus,  the cardiac plexus, and the pulmonary plexus.
+The left vagus nerve also gives rise to the left recurrent laryngeal  nerve,  which  arises  from  it  at  the  inferior margin of the arch of the aorta just lateral to the ligamen-tum arteriosum. The left recurrent laryngeal nerve passes inferior to the arch of the aorta before ascending on its medial surface. Entering a groove between the trachea and esophagus, the left recurrent laryngeal nerve continues
+
+
+
+
+
+
+Esophagus
+
+
+
+Left subclavian artery
+
+
+
+Left phrenic nerve
+
+Ligamentum arteriosum
+
+Left vagus nerve
+
+Left recurrent laryngeal nerve
+
+Left pulmonary artery
+
+
+Bronchus
+
+
+
+
+
+Thoracic aorta
+
+
+Pericardial sac
+
+
+Diaphragm
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 3.95  Left vagus nerve passing through the superior mediastinum.	225
+Thorax
+
+
+
+superiorly to enter the neck and terminate in the larynx (Fig. 3.96).
+
+Phrenic nerves
+The phrenic nerves arise in the cervical region mainly from the fourth, but also from the third and fifth, cervical spinal cord segments.
+The  phrenic  nerves  descend  through  the  thorax  to supply motor and sensory innervation to the diaphragm and its associated membranes. As they pass through the thorax, they provide innervation through somatic afferent fibers to the mediastinal pleura, fibrous pericardium, and parietal layer of serous pericardium.
+
+Right phrenic nerve
+The right phrenic nerve enters the superior mediastinum lateral to the right vagus nerve and lateral and slightly
+
+posterior to the beginning of the right brachiocephalic vein (see Fig. 3.94). It continues inferiorly along the right side of this vein and the right side of the superior vena cava.
+On entering the middle mediastinum, the right phrenic nerve descends along the right side of the pericardial sac, within the fibrous pericardium, anterior to the root of the right lung. The pericardiacophrenic vessels accompany it through most of its course in the thorax (see Fig. 3.60). It leaves the thorax by passing through the diaphragm with the inferior vena cava.
+
+Left phrenic nerve
+The left phrenic nerve enters the superior mediastinum in a position similar to the path taken by the right phrenic nerve. It lies lateral to the left vagus nerve and lateral and slightly posterior to the beginning of  the left brachioce-phalic vein (see Fig. 3.89), and continues to descend across the left lateral surface of  the arch of  the aorta, passing superficially to the left vagus nerve and the left superior intercostal vein.
+On entering the middle mediastinum, the left phrenic
+
+
+
+Esophagus
+
+
+
+Trachea
+
+
+Left recurrent laryngeal nerve
+
+
+Left subclavian artery
+
+nerve follows the left side of the pericardial sac, within the fibrous pericardium, anterior to the root of the left lung, and is accompanied by the pericardiacophrenic vessels (see Fig. 3.60). It leaves the thorax by piercing the diaphragm near the apex of the heart.
+
+
+
+
+
+
+Left vagus nerve
+
+Right main                                                          Arch of aorta bronchus                                                           Ligamentum
+arteriosum TIV/V
+Left
+vertebral	pulmonary artery
+level
+
+
+
+
+Left main Pulmonary trunk	bronchus
+
+Esophagus	Thoracic aorta
+
+
+
+
+
+
+
+Fig. 3.96  Left recurrent laryngeal nerve passing through the 226	superior mediastinum.
+
+
+In the clinic
+
+The vagus nerves, recurrent laryngeal nerves, and hoarseness
+The left recurrent laryngeal nerve is a branch of the left vagus nerve. It passes between the pulmonary artery and the aorta, a region known clinically as the aortopulmonary window, and may be compressed in any patient with a pathological mass in this region. This compression results in left vocal cord paralysis and hoarseness of the voice. Lymph node enlargement, often associated with the spread of lung cancer, is a common condition that may produce compression. Chest radiography is therefore usually carried out for all patients whose symptoms include a hoarse voice.
+More superiorly, in the root of the neck, the right vagus nerve gives off the right recurrent laryngeal nerve, which “hooks” around the right subclavian artery as it passes over the cervical pleura. If a patient has a hoarse voice and a right vocal cord palsy is demonstrated at laryngoscopy, chest radiography with an apical lordotic view should be obtained to assess for cancer in the right lung apex (Pancoast’s tumor).
+Regional Anatomy  •  Mediastinum	3
+
+
+Thoracic duct in the superior mediastinum
+The thoracic duct, which is the major lymphatic vessel in the body, passes through the posterior portion of the supe-rior mediastinum (see Figs. 3.87 and 3.92). It:
+
+
+The esophagus has a slight anterior-to-posterior curva-ture that parallels the thoracic portion of  the vertebral column, and is secured superiorly by its attachment to the  pharynx  and  inferiorly  by  its  attachment  to  the
+
+
+
+
+■     enters the superior mediastinum inferiorly, slightly to the left of the midline, having moved to this position just before leaving the posterior mediastinum opposite ver-tebral level TIV/V; and
+■     continues through the superior mediastinum, posterior to the arch of the aorta, and the initial portion of the left subclavian artery, between the esophagus and the left mediastinal part of the parietal pleura.
+
+diaphragm.
+
+Relationships to important structures in the posterior mediastinum
+In the posterior mediastinum, the esophagus is related to a number of important structures. The right side is covered by the mediastinal part of the parietal pleura.
+Posterior to the esophagus, the thoracic duct is on the right side inferiorly, but crosses to the left more superiorly.
+
+
+
+
+Posterior mediastinum
+The posterior mediastinum is posterior to the pericardial sac and diaphragm and anterior to the bodies of the mid and lower thoracic vertebrae (see Fig. 3.57).
+
+Also on the left side of the esophagus is the thoracic aorta. Anterior to the esophagus, below the level of the tra-cheal bifurcation, are the right pulmonary artery and the left main bronchus. The esophagus then passes immedi-ately posteriorly to the left atrium, separated from it only
+
+
+
+
+■     Its superior boundary is a transverse plane passing from the sternal angle to the intervertebral disc between vertebrae TIV and TV.
+■     Its inferior boundary is the diaphragm.
+■     Laterally, it is bordered by the mediastinal part of pari-etal pleura on either side.
+■     Superiorly,   it   is   continuous   with   the   superior mediastinum.
+
+by pericardium. Inferior to the left atrium, the esophagus is related to the diaphragm.
+Structures other than the thoracic duct posterior to the esophagus include portions of the hemiazygos veins, the right posterior intercostal vessels, and, near the diaphragm, the thoracic aorta.
+The esophagus is a flexible, muscular tube that can be compressed or narrowed by surrounding structures at four locations (Fig. 3.98):
+
+
+
+Major   structures   in   the   posterior   mediastinum include the:
+
+■     the junction of  the esophagus with the pharynx in the neck;
+■     in the superior mediastinum where the esophagus is
+
+
+
+■     esophagus and its associated nerve plexus, ■     thoracic aorta and its branches,
+■     azygos system of veins,
+■     thoracic duct and associated lymph nodes, ■     sympathetic trunks, and
+■     thoracic splanchnic nerves.
+
+crossed by the arch of the aorta;
+■     in the posterior mediastinum where the esophagus is compressed by the left main bronchus;
+■     in the posterior mediastinum at the esophageal hiatus in the diaphragm.
+
+
+
+
+Esophagus
+The esophagus is a muscular tube passing between the pharynx in the neck and the stomach in the abdomen. It begins at the inferior border of the cricoid cartilage, oppo-site vertebra CVI, and ends at the cardiac opening of the stomach, opposite vertebra TXI.
+The esophagus descends on the anterior aspect of the bodies of the vertebrae, generally in a midline position as it moves through the thorax (Fig. 3.97). As it approaches the diaphragm, it moves anteriorly and to the left, crossing from the right side of  the thoracic aorta to eventually assume a position anterior to it. It then passes through the esophageal hiatus, an opening in the muscular part of the diaphragm, at vertebral level TX.
+
+These  constrictions  have  important  clinical  conse-quences. For example, a swallowed object is most likely to lodge at a constricted area. An ingested corrosive substance would  move  more  slowly  through  a  narrowed  region, causing more damage at this site than elsewhere along the esophagus. Also, constrictions present problems during the passage of medical instruments.
+
+Arterial supply and venous and lymphatic drainage
+The arterial supply and venous drainage of  the esopha-gus in the posterior mediastinum involve many vessels. Esophageal arteries arise from the thoracic aorta, bronchial arteries, and ascending branches of the left gastric artery
+in the abdomen.	227
+Thorax
+
+
+Esophagus
+Trachea	Left common carotid artery
+
+Left subclavian artery
+
+
+
+
+Brachiocephalic trunk
+
+
+Arch of aorta
+
+Right main bronchus
+Left main bronchus
+
+
+
+Esophagus	Thoracic aorta
+
+
+
+
+
+
+Diaphragm
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 3.97  Esophagus.
+
+
+Venous drainage involves small vessels returning to the azygos vein, hemiazygos vein, and esophageal branches to the left gastric vein in the abdomen.
+Lymphatic drainage of the esophagus in the posterior mediastinum  returns  to  posterior  mediastinal  and  left gastric nodes.
+
+Innervation
+Innervation  of  the  esophagus,  in  general,  is  complex. Esophageal  branches  arise  from  the  vagus  nerves  and sympathetic trunks.
+Striated muscle fibers in the superior portion of  the esophagus originate from the branchial arches and are
+228	innervated by branchial efferents from the vagus nerves.
+
+Smooth muscle fibers are innervated by cranial compo-nents of the parasympathetic part of the autonomic divi-sion of  the peripheral nervous system, visceral efferents from the vagus nerves. These are preganglionic fibers that synapse in the myenteric and submucosal plexuses of the enteric nervous system in the esophageal wall.
+Sensory innervation of the esophagus involves visceral afferent fibers originating in the vagus nerves, sympathetic trunks, and splanchnic nerves.
+The  visceral  afferents  from  the  vagus  nerves  are involved  in  relaying  information  back  to  the  central nervous system about normal physiological processes and reflex activities. They are not involved in the relay of pain recognition.
+Regional Anatomy  •  Mediastinum	3
+
+
+
+Pharynx
+
+
+Esophagus
+
+
+Junction of esophagus with pharynx
+
+
+Esophagus
+
+
+
+Left vagus nerve
+
+
+Right vagus nerve
+
+Trachea
+
+Where esophagus is crossed by arch of aorta
+Where esophagus is compressed by left main bronchus
+
+
+Position of esophagus posterior to left atrium
+
+
+At the esophageal hiatus
+
+Diaphragm	Anterior vagal trunk
+
+
+Esophageal
+plexus	Stomach
+
+
+
+
+Posterior vagal trunk
+Fig. 3.98  Sites of normal esophageal constrictions.
+
+
+
+
+The visceral afferents that pass through the sympathetic trunks and the splanchnic nerves are the primary partici-pants in detection of esophageal pain and transmission of this information to various levels of the central nervous system.
+
+
+
+Fig. 3.99  Esophageal plexus.
+
+
+
+Esophageal plexus
+After passing posteriorly to the root of the lungs, the right and left vagus nerves approach the esophagus. As they reach  the  esophagus,  each  nerve  divides  into  several branches  that  spread  over  this  structure,  forming  the esophageal plexus (Fig. 3.99). There is some mixing of fibers from the two vagus nerves as the plexus continues
+
+■     the anterior vagal trunk on the anterior surface of the esophagus, mainly from fibers originally in the left vagus nerve;
+■     the posterior vagal trunk on the posterior surface of the esophagus, mainly from fibers originally in the right vagus nerve.
+
+inferiorly on the esophagus toward the diaphragm. Just	The  vagal  trunks  continue  on  the  surface  of   the
+
+above the diaphragm, fibers of the plexus converge to form two trunks:
+
+esophagus as it passes through the diaphragm into the abdomen.
+
+
+
+
+
+
+229
+Thorax
+
+
+
+In the clinic
+
+Esophageal cancer
+When patients present with esophageal cancer, it is important to note which portion of the esophagus contains the tumor because tumor location determines the sites to which the disease will spread (Fig. 3.100).
+Esophageal cancer spreads quickly to lymphatics, draining to lymph nodes in the neck and around the celiac artery. Endoscopy or barium swallow is used to assess the site. CT and MRI may be necessary to stage the disease.
+Once the extent of the disease has been assessed, treatment can be planned.
+
+Right lung	Aorta	Left lung
+
+In the clinic
+
+Esophageal rupture
+The first case of esophageal rupture was described by Herman Boerhaave in 1724. This case was fatal, but early diagnosis has increased the survival rate up to 65%. If the disease is left untreated, mortality is 100%.
+Typically, the rupture occurs in the lower third of the esophagus with a sudden rise in intraluminal
+esophageal pressure produced by vomiting secondary to an uncoordination and failure of the cricopharyngeus muscle to relax. Because the tears typically occur on the left, they are often associated with a large left pleural effusion that contains the gastric contents. In some patients, subcutaneous emphysema may be demonstrated.
+Treatment is optimal with urgent surgical repair.
+
+
+
+
+
+
+
+Thoracic aorta
+The thoracic portion of  the descending aorta (thoracic aorta) begins at the lower edge of vertebra TIV, where it is continuous with the arch of the aorta. It ends anterior to the lower edge of vertebra TXII, where it passes through the  aortic  hiatus  posterior  to  the  diaphragm.  Situated to the left of the vertebral column superiorly, it approaches the midline inferiorly, lying directly anterior to the lower
+Trachea	Esophageal cancer	thoracic  vertebral  bodies  (Fig.  3.101).  Throughout  its
+
+
+Fig. 3.100  Axial CT showing esophageal cancer.
+
+course, it gives off a number of branches, which are sum-marized in Table 3.3.
+
+
+
+
+
+Table 3.3
+
+Branches
+
+Branches of the thoracic aorta
+
+Origin and course
+
+
+
+Pericardial branches Bronchial branches
+
+Esophageal branches
+
+
+Mediastinal branches
+
+Posterior intercostal arteries
+
+
+Superior phrenic arteries
+
+230	Subcostal artery
+
+A few small vessels to the posterior surface of the pericardial sac
+Vary in number, size, and origin—usually, two left bronchial arteries from the thoracic aorta and one right bronchial artery from the third posterior intercostal artery or the superior left bronchial artery
+Four or five vessels from the anterior aspect of the thoracic aorta, which form a continuous anastomotic chain—anastomotic connections include esophageal branches of the inferior thyroid artery superiorly, and esophageal branches of the left inferior phrenic and the left gastric arteries inferiorly
+Several small branches supplying lymph nodes, vessels, nerves, and areolar tissue in the posterior mediastinum
+Usually, nine pairs of vessels branching from the posterior surface of the thoracic aorta—usually supply lower nine intercostal spaces (first two spaces are supplied by the supreme intercostal artery—a branch of the costocervical trunk)
+Small vessels from the lower part of the thoracic aorta supplying the posterior part of the superior surface of the diaphragm—they anastomose with the musculophrenic and pericardiacophrenic arteries
+The lowest pair of branches from the thoracic aorta located inferior to rib XII
+Regional Anatomy  •  Mediastinum	3
+
+
+Trachea	Left subclavian artery	There is significant variation in the origin, course, tribu-
+
+
+Supreme intercostal artery
+
+Right bronchial artery
+
+
+Esophagus	Arch of aorta
+
+Superior left bronchial artery
+
+taries, anastomoses, and termination of these vessels.
+
+Azygos vein
+The azygos vein arises opposite vertebra LI or LII at the junction between the right ascending lumbar vein and the right subcostal vein (Fig. 3.102). It may also arise as a direct branch of the inferior vena cava, which is joined by a common trunk from the junction of the right ascend-ing lumbar vein and the right subcostal vein.
+The azygos vein enters the thorax through the aortic hiatus of the diaphragm, or it enters through or posterior to the right crus of the diaphragm. It ascends through the posterior mediastinum, usually to the right of the thoracic duct. At approximately vertebral level TIV, it arches anteri-orly, over the root of the right lung, to join the superior vena cava before the superior vena cava enters the pericar-dial sac.
+Tributaries of the azygos vein include:
+
+
+
+
+
+
+
+Posterior intercostal arteries
+
+
+
+
+
+Esophageal branches
+
+Esophagus
+
+
+
+
+
+Mediastinal branches
+
+■     the right superior intercostal vein (a single vessel formed by the junction of the second, third, and fourth intercostal veins),
+■     fifth to eleventh right posterior intercostal veins, ■     the hemiazygos vein,
+■     the accessory hemiazygos vein, ■     esophageal veins,
+■     mediastinal veins,
+
+
+
+Fig. 3.101  Thoracic aorta and branches.	■
+■
+
+pericardial veins, and right bronchial veins.
+
+
+Azygos system of veins
+The azygos system of veins consists of a series of longitu-	Hemiazygos vein
+dinal vessels on each side of the body that drain blood from	The  hemiazygos   vein  (inferior   hemiazygos   vein)
+
+the body wall and move it superiorly to empty into the superior vena cava. Blood from some of the thoracic viscera may also enter the system, and there are anastomotic con-nections with abdominal veins.
+The longitudinal vessels may or may not be continuous and are connected to each other from side to side at various points throughout their course (Fig. 3.102).
+The  azygos  system  of  veins  serves  as  an  important anastomotic pathway capable of returning venous blood from the lower part of the body to the heart if the inferior vena cava is blocked.
+The major veins in the system are:
+
+usually arises at the junction between the left ascending lumbar vein and the left subcostal vein (Fig. 3.102). It may also arise from either of these veins alone and often has a connection to the left renal vein.
+The hemiazygos vein usually enters the thorax through the left crus of the diaphragm, but may enter through the aortic hiatus. It ascends through the posterior mediastinum, on the left side, to approximately vertebral level TIX. At this point, it crosses the vertebral column, posterior to the thoracic aorta, esophagus, and thoracic duct, to enter the azygos vein.
+Tributaries joining the hemiazygos vein include:
+
+
+
+■     the azygos vein, on the right; and
+■     the hemiazygos vein and the accessory hemiazygos vein, on the left.
+
+■     the lowest four or five left posterior intercostal veins, ■     esophageal veins, and
+■     mediastinal veins.
+
+
+231
+Thorax
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Right superior intercostal vein	Left superior intercostal vein
+
+Opening of azygos vein into superior vena cava
+
+
+
+Accessory hemiazygos Azygos vein	vein
+
+
+
+Posterior intercostal vein
+
+
+
+
+
+Hemiazygos vein
+
+
+
+Right subcostal vein
+
+
+Right ascending lumbar vein	Ascending lumbar vein
+
+Inferior vena cava
+
+
+
+
+
+
+Fig. 3.102  Azygos system of veins.
+
+
+
+
+
+
+
+
+
+232
+Regional Anatomy  •  Mediastinum	3
+
+
+Accessory hemiazygos vein
+The accessory hemiazygos vein (superior hemiazygos vein) descends on the left side from the superior portion of the posterior mediastinum to approximately vertebral level TVIII (Fig. 3.102). At this point, it crosses the vertebral column to join the azygos vein, or ends in the hemiazygos vein, or has a connection to both veins. Usually, it also has a connection superiorly to the left superior intercostal vein.
+Vessels that drain into the accessory hemiazygos vein include:
+
+Thoracic duct in the posterior mediastinum
+The thoracic duct is the principal channel through which lymph from most of the body is returned to the venous system. It begins as a confluence of lymph trunks in the abdomen, sometimes forming a saccular dilation referred to as the cisterna chyli (chyle cistern), which drains the abdominal viscera and walls, pelvis, perineum, and lower limbs.
+The thoracic duct extends from vertebra LII to the root of the neck.
+Entering the thorax, posterior to the aorta, through the aortic hiatus of the diaphragm, the thoracic duct ascends
+
+
+
+
+■     the fourth to eighth left posterior intercostal veins, and ■     sometimes, the left bronchial veins.
+
+through the posterior mediastinum to the right of midline between the thoracic aorta on the left and the azygos vein on the right (Fig. 3.103). It lies posterior to the diaphragm
+
+
+Esophagus
+
+Thoracic duct
+
+
+Right common carotid artery
+
+
+
+
+
+Superior vena cava
+
+
+
+Azygos vein
+
+Left brachiocephalic vein
+
+
+
+Accessory hemiazygos vein
+
+
+
+
+
+
+
+
+
+Hemiazygos vein
+Thoracic duct
+
+
+
+
+
+
+
+
+
+
+
+Cisterna chyli
+
+
+
+
+Fig. 3.103  Thoracic duct.	233
+Thorax
+
+
+
+and  the  esophagus  and  anterior  to  the  bodies  of  the vertebrae.
+At vertebral level TV, the thoracic duct moves to the left of midline and enters the superior mediastinum. It contin-
+
+■     upper intercostal lymph trunks draining the upper left five or six intercostal spaces,
+■     ducts from posterior mediastinal nodes, and ■     ducts from posterior diaphragmatic nodes.
+
+ues through the superior mediastinum and into the neck. After being joined, in most cases, by the left jugular
+trunk, which drains the left side of the head and neck, and the left subclavian trunk, which drains the left upper limb, the thoracic duct empties into the junction of the left subclavian and left internal jugular veins.
+The thoracic duct usually receives the contents from:
+
+
+Sympathetic trunks
+The sympathetic trunks are an important component of the sympathetic part of the autonomic division of the peripheral nervous system and are usually considered a component  of  the  posterior  mediastinum  as  they  pass through the thorax.
+This portion of the sympathetic trunks consists of two
+
+
+
+■     the confluence of lymph trunks in the abdomen,
+■     descending thoracic lymph trunks draining the lower six or seven intercostal spaces on both sides,
+
+parallel cords punctuated by 11 or 12 ganglia (Fig. 3.104). The  ganglia  are  connected  to  adjacent  thoracic  spinal nerves by white and gray rami communicantes and are
+
+
+
+
+
+TI
+
+
+Sympathetic ganglion
+
+
+
+Sympathetic trunk
+TV
+
+
+
+Gray and white rami communicantes
+
+Intercostal nerve (anterior ramus of thoracic spinal nerve)
+
+
+
+Greater splanchnic nerve
+
+Lesser splanchnic nerve
+
+Least splanchnic nerve
+
+
+
+
+
+
+
+
+
+234	Fig. 3.104  Thoracic portion of sympathetic trunks.
+Regional Anatomy  •  Mediastinum	3
+
+
+numbered according to the thoracic spinal nerve with           The second type, which includes branches from the which they are associated.                                                            lower  seven  ganglia,  consists  mainly  of  preganglionic
+
+In the superior portion of the posterior mediastinum, the trunks are anterior to the neck of the ribs. Inferiorly, they become more medial in position until they lie on the lateral aspect of  the vertebral bodies. The sympathetic trunks leave the thorax by passing posterior to the dia-
+
+sympathetic fibers, which supply the various abdominal and pelvic viscera. These branches are large, also carry visceral  afferent  fibers,  and  form  the  three  thoracic splanchnic nerves referred to as the greater, lesser, and least splanchnic nerves (Fig. 3.104).
+
+
+
+phragm under the medial arcuate ligament or through the crura  of  the  diaphragm. Throughout  their  course  the trunks are covered by parietal pleura.
+
+Branches from the ganglia
+Two types of medial branches are given off by the ganglia:
+
+
+■     The greater splanchnic nerve on each side usually arises from the fifth to ninth or tenth thoracic ganglia. It descends across the vertebral bodies moving in a medial  direction,  passes  into  the  abdomen  through the  crus  of  the  diaphragm,  and  ends  in  the  celiac ganglion.
+
+
+
+■     The first type includes branches from the upper five ganglia.
+■     The second type includes branches from the lower seven ganglia.
+
+■     The lesser splanchnic nerve usually arises from the ninth and tenth, or tenth and eleventh thoracic ganglia. It descends across the vertebral bodies moving in a medial direction, and passes into the abdomen through the crus of  the diaphragm to end in the aorticorenal
+
+
+
+The first type, which includes branches from the upper five ganglia, consists mainly of postganglionic sympathetic fibers, which supply the various thoracic viscera. These branches are relatively small, and also contain visceral afferent fibers.
+
+ganglion.
+■     The  least  splanchnic  nerve  (lowest  splanchnic nerve) usually arises from the twelfth thoracic ganglion. It descends and passes into the abdomen through the crus of the diaphragm to end in the renal plexus.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+235
+Thorax
+
+
+Surface anatomy
+
+Thorax surface anatomy	structures.  To  determine  the  location  of  specific  ribs,
+
+The ability to visualize how anatomical structures in the thorax are related to surface features is fundamental to a physical examination. Landmarks on the body’s surface
+
+palpate the jugular notch at the superior extent of the manubrium of the sternum. Move down the sternum until a ridge is felt. This ridge is the sternal angle, which identi-
+
+can be used to locate deep structures and to assess function	fies  the  articulation  between  the  manubrium  of   the
+
+by auscultation and percussion.
+
+How to count ribs
+Knowing how to count ribs is important because different ribs provide palpable landmarks for the positions of deeper
+
+
+
+
+
+Jugular notch
+
+Sternoclavicular joint
+
+sternum and the body of the sternum. The costal cartilage of  rib II articulates with the sternum at this location. Identify rib II. Then continue counting the ribs, moving in a downward and lateral direction (Fig. 3.105).
+
+
+
+
+
+
+
+Clavicle
+
+
+
+Rib I
+Manubrium of sternum	II
+Body of sternum	 III IV
+V Xiphoid process	VI
+VII
+VIII Rib X	IX
+
+
+Coracoid process
+Sternal angle
+
+
+
+Costal cartilage
+
+
+Costal margin
+
+
+
+A
+
+Jugular notch
+Sternoclavicular joint	Clavicle
+
+
+Rib I
+Manubrium of sternum	II
+Body of sternum	 III IV
+
+V
+Xiphoid process	VI
+
+VII
+VIII Rib X	IX
+
+
+Coracoid process
+Sternal angle
+
+
+
+Costal cartilage
+
+
+Costal margin
+
+
+B
+
+Fig. 3.105  Anterior view of chest wall with the locations of skeletal structures shown. A. In women. The location of the nipple relative to a specific intercostal space varies depending on the size of the breasts, which may not be symmetrical. B. In men. Note the location of the nipple
+236	in the fourth intercostal space.
+Surface Anatomy  •  Visualizing Structures at the TIV/V Vertebral Level	3
+
+
+
+Surface anatomy of the breast in women
+Although breasts vary in size, they are normally positioned on the thoracic wall between ribs II and VI and overlie the pectoralis major muscles. Each mammary gland extends superolaterally around the lower margin of the pectoralis major  muscle  and  enters  the  axilla  (Fig.  3.106). This portion of the gland is the axillary tail or axillary process. The positions of the nipple and areola vary relative to the chest wall depending on breast size.
+
+Visualizing structures at the TIV/V vertebral level
+
+The TIV/V vertebral level is a transverse plane that passes through the sternal angle on the anterior chest wall and the intervertebral disc between TIV and TV vertebrae pos-teriorly. This plane can easily be located, because the joint between the manubrium of the sternum and the body of the sternum forms a distinct bony protuberance that can be palpated. At the TIV/V level (Fig. 3.107):
+
+
+■     The  costal  cartilage  of  rib  II  articulates  with  the sternum.
+■     The superior mediastinum is separated from the inferior mediastinum.
+■     The ascending aorta ends and the arch of  the aorta begins.
+■     The arch of  the aorta ends and the thoracic aorta begins.
+■     The trachea bifurcates.
+
+A
+
+Areola	Nipple
+
+
+
+Axillary process	TIV/V vertebral level
+
+
+
+
+
+
+
+
+
+
+
+
+
+B
+
+
+Fig. 3.106  A. Close-up view of nipple and surrounding areola of the breast. B. Lateral view of the chest wall of a woman showing the axillary process of the breast.
+
+
+Fig. 3.107  Anterior view of the chest wall of a man showing the locations of various structures related to the TIV/V level.
+
+
+
+
+
+
+
+
+
+237
+Thorax
+
+
+
+
+Visualizing structures in the superior mediastinum
+
+A number of  structures in the superior mediastinum in adults can be visualized based on their positions relative to skeletal landmarks that can be palpated through the skin (Fig. 3.108).
+
+■     The left brachiocephalic vein crosses from left to right behind the manubrium of the sternum.
+■     The brachiocephalic veins unite to form the superior vena cava behind the lower border of the costal cartilage of the right first rib.
+■     The arch of the aorta begins and ends at the transverse plane between the sternal angle anteriorly and vertebral level TIV/V posteriorly. The arch may reach as high as
+
+■     On  each  side,  the  internal  jugular  and  subclavian	the midlevel of the manubrium of the sternum. veins join to form the brachiocephalic veins behind
+the sternal ends of the clavicles near the sternoclavicu-lar joints.
+
+
+
+
+Right common carotid artery	Trachea	Esophagus
+
+
+Right internal jugular vein
+
+
+Right subclavian artery
+
+
+Left common carotid artery
+
+Left internal jugular vein
+Left subclavian artery
+
+
+Left subclavian vein
+
+Right subclavian vein
+
+
+
+Right brachiocephalic vein
+
+Superior vena cava
+
+Right pulmonary artery
+
+
+Right main bronchus
+
+Left brachiocephalic vein
+
+Arch of aorta
+
+Left pulmonary artery
+
+Left main bronchus
+
+
+
+Pulmonary trunk
+
+
+
+
+
+
+
+
+
+Esophagus	Ascending aorta	Thoracic aorta
+
+Fig. 3.108  Anterior view of the chest wall of a man showing the locations of different structures in the superior mediastinum as they relate to the skeleton.
+
+
+
+
+
+238
+Surface Anatomy  •  Visualizing the Margins of the Heart	3
+
+
+
+
+Visualizing the margins of the heart
+Surface landmarks can be palpated to visualize the outline of the heart (Fig. 3.109).
+
+■     The left margin of the heart descends laterally from the second intercostal space to the apex located near the midclavicular line in the fifth intercostal space.
+■     The lower margin of the heart extends from the sternal
+
+
+■     The upper limit of  the heart reaches as high as the third costal cartilage on the right side of the sternum and the second intercostal space on the left side of the sternum.
+■     The right margin of the heart extends from the right third  costal  cartilage  to  near  the  right  sixth  costal cartilage.
+
+end of the right sixth costal cartilage to the apex in the fifth intercostal space near the midclavicular line.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Third costal cartilage
+
+
+
+
+Sixth costal cartilage
+
+Second intercostal space
+
+
+
+
+Fifth intercostal space
+
+
+
+
+
+Midclavicular line
+
+
+
+
+
+Fig. 3.109  Anterior view of the chest wall of a man showing skeletal structures and the surface projection of the heart.
+
+
+
+
+
+
+
+
+
+
+
+239
+Thorax
+
+
+
+
+Where to listen for heart sounds
+To listen for valve sounds, position the stethoscope down-
+
+Superiorly, the parietal pleura projects above the first costal cartilage. Anteriorly, the costal pleura approaches the midline posterior to the upper portion of the sternum.
+
+stream  from  the  flow  of   blood  through  the  valves       Posterior to the lower portion of  the sternum, the left (Fig. 3.110).                                                                                   parietal pleura does not come as close to the midline as it
+
+
+■     The tricuspid valve is heard just to the left of the lower part of the sternum near the fifth intercostal space.
+■     The mitral valve is heard over the apex of the heart in the left fifth intercostal space at the midclavicular line.
+■     The pulmonary valve is heard over the medial end of the left second intercostal space.
+■     The aortic valve is heard over the medial end of the right second intercostal space.
+
+does on the right side. This is because the heart bulges onto the left side (Fig. 3.111A).
+Inferiorly, the pleura reflects onto the diaphragm above the costal margin and courses around the thoracic wall following an VIII, X, XII contour (i.e., rib VIII in the mid-clavicular line, rib X in the midaxillary line, and vertebra TXII posteriorly).
+The lungs do not completely fill the area surrounded by   the   pleural   cavities,   particularly   anteriorly   and
+
+
+
+
+Visualizing the pleural cavities and lungs, pleural recesses, and lung lobes and fissures
+
+Palpable surface landmarks can be used to visualize the
+
+inferiorly.
+
+■     Costomediastinal recesses occur anteriorly, particularly on the left side in relationship to the heart bulge.
+
+
+
+normal  outlines  of  the  pleural  cavities  and  the  lungs and to determine the positions of  the pulmonary lobes and fissures.
+
+■     Costodiaphragmatic recesses occur inferiorly between the lower lung margin and the lower margin of  the pleural cavity.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Auscultation position for aortic valve
+
+Aortic valve
+
+
+
+Tricuspid valve
+
+
+
+
+
+
+
+
+
+
+Auscultation position for tricuspid valve
+
+
+Auscultation position for pulmonary valve
+
+Pulmonary valve
+
+
+
+
+Mitral valve
+
+
+
+
+
+
+
+
+
+
+Auscultation position for mitral valve
+
+
+240	Fig. 3.110  Anterior view of the chest wall of a man showing skeletal structures, heart, location of the heart valves, and auscultation points.
+Surface Anatomy  •  Visualizing the Pleural Cavities and Lungs, Pleural Recesses, and Lung Lobes and Fissures	3
+
+
+
+
+
+
+
+
+
+
+
+Superior lobe
+
+Horizontal fissure
+
+Middle lobe
+
+Rib VI Inferior lobe
+
+Rib VIII
+
+Superior lobe
+
+
+
+Costomediastinal recess
+
+Inferior lobe
+
+Costodiaphragmatic recess
+
+
+Rib X
+
+
+Parietal pleura
+
+A
+
+
+
+
+
+
+Upper lobe
+
+TIV
+Rib V	Oblique fissure
+Rib VI
+
+
+
+
+TX	Lower lobe Rib X
+
+TXII	Parietal pleura
+
+
+
+B
+
+Fig. 3.111  Views of the chest wall showing the surface projections of the lobes and the fissures of the lungs. A. Anterior view in a woman. On the right side, the superior, middle, and inferior lobes are illustrated. On the left side, the superior and inferior lobes are illustrated.
+B. Posterior view in a woman. On both sides, the superior and inferior lobes are illustrated. The middle lobe on the right side is not visible in this view.
+
+
+
+
+241
+Thorax
+
+
+
+In quiet respiration, the inferior margin of  the lungs travels around the thoracic wall following a VI, VIII, X contour (i.e., rib VI in the midclavicular line, rib VIII in the midaxillary line, and vertebra TX posteriorly).
+In the posterior view, the oblique fissure on both sides is located in the midline near the spine of  vertebra TIV (Figs. 3.111B and 3.112A). It moves laterally in a down-ward direction, crossing the fourth and fifth intercostal spaces and reaches rib VI laterally.
+
+In the anterior view, the horizontal fissure on the right side follows the contour of rib IV and its costal cartilage and the oblique fissures on both sides follow the contour of rib VI and its costal cartilage (Fig. 3.112B).
+
+
+Where to listen for lung sounds
+The stethoscope placements for listening for lung sounds are shown in Fig. 3.113.
+
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+TIV spine		Superior lobe Oblique fissure
+
+Medial margin of scapula
+
+Superior lobe TIV spine
+Rib V
+Rib VI Middle lobe
+Inferior lobe Rib VIII
+
+Rib X
+Midaxillary line
+
+
+
+
+Horizontal fissure Oblique fissure
+
+Parietal pleura Costodiaphragmatic recess
+
+A	Inferior lobe	B
+
+Fig. 3.112  Views of the chest wall. A. Posterior view in a woman with arms abducted and hands positioned behind her head. On both sides, the superior and inferior lobes of the lungs are illustrated. When the scapula is rotated into this position, the medial border of the scapula parallels the position of the oblique fissure and can be used as a guide for determining the surface projection of the superior and inferior lobes of the lungs. B. Lateral view in a man with his right arm abducted. The superior, middle, and inferior lobes of the right lung are illustrated. The oblique fissure begins posteriorly at the level of the spine of vertebra TIV, passes inferiorly crossing rib IV, the fourth intercostal space, and rib V. It crosses the fifth intercostal space at the midaxillary line and continues anteriorly along the contour of rib VI. The horizontal fissure crosses rib V in the midaxillary space and continues anteriorly, crossing the fourth intercostal space and following the contour of rib IV and its costal cartilage to the sternum.
+
+
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+
+
+
+242
+Surface Anatomy  •  Where to Listen for Lung Sounds	3
+
+
+
+
+
+
+
+
+I
+Apex of right lung	II		Superior lobe of right lung III
+
+IV
+V VI VII
+VIII IX X
+
+
+
+
+
+
+
+Middle lobe of right lung	Inferior lobe of right lung A
+
+
+
+
+I
+II
+III
+IV
+V Apex of left lung	VI
+VII
+VIII IX
+X XI
+XII
+
+
+
+
+
+
+
+
+
+
+
+Superior lobe of left lung
+
+
+
+
+
+
+
+
+
+Inferior lobe of left lung B
+
+Fig. 3.113  Views of the chest wall of a man with stethoscope placements for listening to the lobes of the lungs. A. Anterior views. B. Posterior views.
+
+243
+Thorax
+
+
+Clinical cases
+
+
+Case 1
+
+MYOCARDIAL INFARCTION
+
+A 65-year-old man was admitted to the emergency room with severe central chest pain that radiated to the neck and predominantly to the left arm. He was overweight and a known heavy smoker.
+
+On examination he appeared gray and sweaty. His blood pressure was 74/40 mm Hg (normal range
+120/80 mm Hg). An electrocardiogram (ECG) was performed and demonstrated anterior myocardial infarction. An urgent echocardiograph demonstrated poor left ventricular function. The cardiac angiogram revealed an occluded vessel (Fig. 3.114A,B). Another approach to evaluating coronary arteries in patients is to perform maximum intensity projection (MIP) CT studies (Fig. 3.115A,B).
+
+
+
+and TIV levels. At this level, somatic afferent nerves from spinal nerves T1 to T4 also enter the spinal cord via the posterior roots. Both types of afferents (visceral and somatic) synapse with interneurons, which then synapse with second neurons whose fibers pass across the cord and then ascend to the somatosensory areas of the brain that represent the T1 to T4 levels. The brain is unable to distinguish clearly between the visceral sensory distribution and the somatic sensory distribution and therefore the pain is interpreted as arising from the somatic regions rather than the visceral organ (i.e., the heart; Fig. 3.114C).
+
+The patient was breathless because his left ventricular function was poor.
+
+When the left ventricle fails, it produces two effects.
+
+
+
+This patient underwent an emergency coronary artery bypass graft and made an excellent recovery. He has now lost weight, stopped smoking, and exercises regularly.
+
+When cardiac cells die during a myocardial infarction, pain fibers (visceral afferents) are stimulated. These visceral sensory fibers follow the course of sympathetic fibers that innervate the heart and enter the spinal cord between the TI
+
+■     First, the contractile force is reduced. This reduces the pressure of the ejected blood and lowers the blood pressure.
+■     The left atrium has to work harder to fill the failing left ventricle. This extra work increases left atrial pressure, which is reflected in an increased pressure in the pulmonary veins, and this subsequently creates a higher
+
+
+
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+
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+
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+
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+
+
+
+
+A	B
+
+Fig. 3.114  A. Normal left coronary artery angiogram. B. Left coronary artery angiogram showing decreased flow due to blockages.
+
+
+
+
+244
+Clinical Cases  •  Case 1	3
+
+
+
+Case 1—cont’d
+
+
+
+
+
+
+
+
+Pain interpreted as originating in distribution of somatic sensory nerves
+
+
+
+
+
+
+
+
+
+
+
+Visceral sensory nerve
+Somatic sensory nerve
+
+T2 T3
+
+
+
+pulmonary venular pressure. This rise in pressure will cause fluid to leak from the capillaries into the pulmonary interstitium and then into the alveoli. Such fluid is called pulmonary edema and it markedly restricts gas exchange. This results in shortness of breath.
+
+This man had a blocked left coronary artery, as shown in Fig. 3.114B.
+
+It is important to know which coronary artery is blocked.
+
+■     The left coronary artery supplies the majority of the left side of the heart. The left main stem vessel is
+approximately 2 cm long and divides into the circumflex artery, which lies between the atrium and the ventricle in the coronary sulcus, and the anterior interventricular artery, which is often referred to as the left anterior descending artery (LAD).
+■     When the right coronary artery is involved with arterial disease and occludes, associated disorders of cardiac rhythm often result because the sinu-atrial and the atrioventricular nodes derive their blood supplies predominantly from the right coronary artery.
+
+When this patient sought medical care, his myocardial function was assessed using ECG, echocardiography, and angiography.
+
+During a patient’s initial examination, the physician will usually assess myocardial function.
+
+T4	After obtaining a clinical history and carrying out a physical examination, a differential diagnosis for the cause of the malfunctioning heart is made. Objective assessment of myocardial and valve function is obtained in the following
+T1	ways:
+
+
+Patient perceives diffuse pain in
+T1–4 dermatomes
+
+C
+
+Fig. 3.114, cont’d  C. Mechanism for perceiving heart pain in T1–4 dermatomes.
+
+■     ECG/EKG (electrocardiography)—a series of electrical traces taken around the long and short axes of the heart that reveal heart rate and rhythm and conduction defects. In addition, it demonstrates the overall function of the right and left sides of the heart and points of dysfunction. Specific changes in the ECG relate to the areas of the heart that have been involved in a myocardial infarction. For example, a right coronary artery occlusion produces infarction in the area of myocardium it supplies, which
+
+(continues)
+
+
+
+
+
+
+
+
+
+
+245
+Thorax
+
+
+Case 1—cont’d
+
+
+is predominantly the inferior aspect; the infarct is therefore called an inferior myocardial infarction. The ECG changes are demonstrated in the leads that visualize the inferior aspect of the myocardium (namely, leads II, III, and aVF).
+■     Chest radiography—reveals the size of the heart and chamber enlargement. Careful observation of the lungs will demonstrate excess fluid (pulmonary edema), which builds up when the left ventricle fails and can produce marked respiratory compromise and death unless promptly treated.
+■     Blood tests—the heart releases enzymes during myocardial infarction, namely lactate dehydrogenase (LDH), creatine kinase (CK), and aspartate transaminase (AST). These plasma enzymes are easily measured in the hospital laboratory and used to determine the diagnosis at an early stage. Further specific enzymes termed isoenzymes can also be determined (creatine kinase MB isoenzyme [CKMB]). Newer tests include an assessment for troponin (a specific component of the myocardium), which is released when cardiac cells die during myocardial infarction.
+
+■     Exercise testing—patients are connected to an ECG monitor and exercised on a treadmill. Areas of ischemia, or poor blood flow, can be demonstrated, so localizing the vascular abnormality.
+■     Nuclear medicine—thallium (a radioactive X-ray emitter) and its derivatives are potassium analogs. They are used to determine areas of coronary ischemia. If no areas of myocardial uptake are demonstrated when these substances are administered to a patient the myocardium is dead.
+■     Coronary angiography—small arterial catheters are maneuvered from a femoral artery puncture site through the femoral artery and aorta and up to the origins of the coronary vessels. X-ray contrast medium is then injected to demonstrate the coronary vessels and their important branches. If there is any narrowing (stenosis), angioplasty may be carried out. In angioplasty tiny balloons are passed across the narrowed areas and inflated to refashion the vessel and so prevent further coronary ischemia and myocardial infarction.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A	B
+
+Fig. 3.115  Axial maximum intensity projection (MIP) CT image through the heart. A. Normal anterior interventricular (left anterior descending) artery. B. Stenotic (calcified) anterior interventricular (left anterior descending) artery.
+
+
+
+
+
+
+
+
+
+246
+Clinical Cases  •  Case 2	3
+
+
+
+Case 2
+
+PULMONARY EMBOLISM
+
+A 53-year-old man presented to the emergency department with a 5-hour history of sharp pleuritic chest pain and shortness of breath. The day before he was on a long haul flight, returning from his holidays. He was usually fit and well and was a keen mountain climber. He had no previous significant medical history.
+
+On physical examination his lungs were clear, he was tachypneic at 24/min, and his saturation was reduced to 92% on room air. Pulmonary embolism was suspected and the patient was referred for a CT pulmonary angiogram. The study demonstrated clots within the right and left main pulmonary arteries. There was no pleural effusion, lung collapse, or consolidation.
+
+He was immediately started on subcutaneous enoxaparin and converted to oral anticoagulation over the course of a couple of days. The whole treatment lasted 6 months as no other risk factors (except immobilization during a long haul flight) were identified. There were no permanent sequelae.
+
+
+
+The embolic material usually originates in the peripheral deep veins of the lower limbs and less commonly in the pelvic, renal, or upper limb deep veins. The material gets detached from the main thrombus in the deep veins and travels into the pulmonary circulation, where it can lodge either in the pulmonary trunk and main pulmonary arteries, giving rise to central pulmonary embolism or in the lobar, segmental, or subsegmental branches, giving rise to peripheral embolism.
+
+The gravity of symptoms is partly dependent on the thrombus load and on which part of the pulmonary arterial tree is affected. Large pulmonary embolisms can lead to severe hemodynamic and respiratory compromise and death (e.g., a saddle thrombus lodged in the pulmonary trunk and in both main pulmonary arteries).
+
+Common risk factors include immobilization, surgery, trauma, malignancy, pregnancy, oral contraceptives, and hereditary factors.
+
+
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+
+
+
+
+247
+Clinical Cases  •  Case 3	3
+
+
+Case 3
+
+CERVICAL RIB	Cervical ribs
+
+A young man has black areas of skin on the tips of his fingers of his left hand. A clinical diagnosis of platelet emboli was made and a source of the emboli sought.
+
+Emboli can arise from many sources. They are clots and plugs of tissue, usually platelets, that are carried from a source to eventually reside in small vessels which they may occlude. Arterial emboli may arise in the heart or in the arteries that supply the region affected. In cases of infected emboli, bacteria grow on the valve and are showered off into the peripheral circulation.
+A neck radiograph and coronal CT image of the neck	A demonstrates a cervical rib (eFig. 3.116).
+
+Cervical ribs may produce three distinct disease entities:
+
+■     Arterial compression and embolization—the cervical rib (or band) on the undersurface of the distal portion of the subclavian artery reduces the diameter of the vessel and allows eddy currents to form. Platelets aggregate and atheroma may develop in this region. This debris can be dislodged and flow distally within the upper limb vessels to block off blood flow to the fingers and the hand, a condition called distal embolization.
+■     Tension on the T1 nerve—the T1 nerve, which normally passes over rib I, is also elevated by the presence of a cervical rib; thus the patient may experience a sensory disturbance over the medial aspect of the forearm, and develop wasting of the intrinsic muscles of the hand.
+■     Compression of the subclavian vein—this may induce axillary vein thrombosis.
+
+A Doppler ultrasound scan revealed marked stenosis of the subclavian artery at the outer border of the rib with abnormal flow distal to the narrowing. Within this region of abnormal flow there was evidence of thrombus adherent to the vessel wall.
+
+This patient underwent surgical excision of the cervical rib and had no further symptoms.
+
+B
+Cervical ribs
+
+eFig. 3.116  Cervical ribs. A. Neck radiograph demonstrating bilateral cervical ribs. B. Coronal computed tomography image showing cervical ribs.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+247.e1
+Thorax
+
+
+
+Case 4 LUNG CANCER
+A 52-year-old man presented with headaches and shortness of breath. He also complained of coughing up small volumes of blood. Clinical examination revealed multiple dilated veins around the neck. A chest radiograph demonstrated an elevated diaphragm on the right and a tumor mass, which was believed to be a primary bronchogenic carcinoma.
+
+By observing the clinical findings and applying anatomical knowledge, the site of the tumor can be inferred.
+
+
+
+
+
+
+Case 5 CHEST WOUND
+A 35-year-old man was shot during an armed robbery. The bullet entry wound was in the right fourth intercostal space, above the nipple. A chest radiograph obtained on admission to the emergency room demonstrated complete collapse of the lung.
+
+A further chest radiograph performed 20 minutes later demonstrated an air/fluid level in the pleural cavity (eFig. 3.117).
+
+
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+
+eFig. 3.117  Chest radiograph demonstrating an air/fluid level in the pleural cavity.
+
+
+
+The multiple dilated veins around the neck are indicative of venous obstruction. The veins are dilated on both sides of the neck, implying that the obstruction must be within a common vessel, the superior vena cava. Anterior to the superior vena cava in the right side of the chest is the phrenic nerve, which supplies the diaphragm. Because the diaphragm is elevated, suggesting paralysis, it is clear that the phrenic nerve has been involved with the tumor.
+
+
+
+
+
+
+
+
+
+
+
+Three common pathological processes may occur in the pleural cavity.
+
+■     If air is introduced into the pleural cavity, a pneumothorax develops and the lung collapses because of its own elastic recoil. The pleural space fills with air, which may further compress the lung. Most patients with a collapsed lung are unlikely to have respiratory impairment. Under certain conditions, air may enter the pleural cavity at such a rate that it shifts and pushes the mediastinum to the opposite side of the chest. This is called tension pneumothorax and is potentially lethal, requiring urgent treatment by insertion of an intercostal tube to remove the air. The commonest causes of pneumothorax are rib fractures and positive pressure ventilation lung damage.
+■     The pleural cavity may fill with fluid (a pleural effusion) and this can be associated with many diseases
+(e.g., lung infection, cancer, abdominal sepsis). It is important to aspirate fluid from these patients to relieve any respiratory impairment and to carry out laboratory tests on the fluid to determine its nature.
+■     Severe chest trauma can lead to development of hemopneumothorax. A tube must be inserted to remove the blood and air that has entered the pleural space and prevent respiratory impairment.
+
+This man needs treatment to drain either the air or fluid or both.
+
+The pleural space can be accessed by passing a needle between the ribs into the pleural cavity. In a normal healthy adult, the pleural space is virtually nonexistent; therefore, any attempt to introduce a needle into this space is unlikely
+
+
+247.e2
+Clinical Cases  •  Case 6	3
+
+
+
+Case 5—cont’d
+
+to succeed and the procedure may damage the underlying lung.
+
+Before any form of chest tube is inserted, the rib must be well anesthetized by infiltration because its periosteum
+is extremely sensitive. The intercostal drain should pass directly on top of the rib. Insertion adjacent to the lower part of the rib may damage the artery, vein, and nerve, which lie within the neurovascular bundle.
+
+Appropriate sites for insertion of a chest drain are either in the fourth or fifth intercostal space between the anterior axillary and midaxillary anatomical lines.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Case 6
+
+BROKEN PACEMAKER
+
+An elderly woman was admitted to the emergency room with severe cardiac failure. She had a left-sided pacemaker box, which had been inserted for a cardiac rhythm disorder (fast atrial fibrillation) many years previously. An ECG demonstrated fast atrial fibrillation. A chest radiograph showed that the wire from the pacemaker had broken under the clavicle.
+
+Anatomical knowledge of this region of the chest explains why the wire broke.
+
+Many patients have cardiac pacemakers. A wire arises from the pacemaker, which lies within the subcutaneous tissue over the pectoralis major muscle and travels from the pacemaker under the skin to pierce the axillary vein just beneath the clavicle, lateral to the subclavius muscle. The wire then passes through the subclavian vein, the brachiocephalic vein, the superior vena cava, and the right atrium, and lies on the wall of the right ventricle (where it can stimulate the heart to contract) (eFig. 3.118). If the wire pierces the axillary vein directly adjacent to the subclavius muscle, it is possible that after many years of shoulder movement the subclavius muscle stresses and breaks the wire, causing the pacemaker to fail. Every effort is made to place the insertion point of the wire as far laterally as feasible within the first part of the axillary vein.
+
+
+
+This position is determined by palpating the sternal angle, which is the point of articulation of rib II. Counting inferiorly will determine the rib number and simple observation will determine the positions of the anterior axillary and midaxillary lines. Insertion of any tube or needle below the fifth interspace runs an appreciable risk of crossing the pleural recesses and placing the needle or the drain into either the liver or the spleen, depending upon which side the needle is inserted.
+
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+eFig. 3.118  Chest radiograph of an individual with a pacemaker. The pacemaker wires (2) can be seen traveling through the venous system to the heart where one ends in the right atrium and the other ends in the right ventricle.
+
+
+
+
+
+247.e3
+Thorax
+
+
+
+Case 7
+
+COARCTATION OF THE AORTA
+
+A 20-year-old man visited his family doctor because he had a cough. A chest radiograph demonstrated translucent notches along the inferior border of ribs III to VI (eFig. 3.119). He was referred to a cardiologist and a diagnosis of coarctation of the aorta was made. The rib notching was caused by dilated collateral intercostal arteries.
+
+Coarctation of the aorta is a narrowing of the aorta distal to the left subclavian artery. This narrowing can markedly reduce blood flow to the lower body. Many of the vessels above the narrowing therefore enlarge due to the increased pressure so that blood can reach the aorta below the level of the narrowing. Commonly, the internal thoracic, superior epigastric, and musculophrenic arteries enlarge anteriorly. These arteries supply the anterior intercostal arteries, which anastomose with the posterior intercostal arteries that allow blood to flow retrogradely into the aorta. Enlargement of the intertcostal vessels results in notching of the ribs.
+
+The first and second posterior intercostal vessels are supplied from the costocervical trunk, which arises from the subclavian artery proximal to the coarctation, so do not enlarge and do not induce rib notching.
+
+
+
+
+
+
+
+Case 8
+
+AORTIC DISSECTION
+
+A 62-year-old man was admitted to the emergency room with severe interscapular pain. His past medical history indicated that he was otherwise fit and well; however, it was noted he was 6’ 9” and had undergone previous eye surgery for dislocating lenses.
+
+On examination the man was pale, clammy, and hypotensive. The pulse in his right groin was weak. An ECG demonstrated an inferior myocardial infarction. Serum blood tests revealed poor kidney function and marked acidosis.
+
+The patient was transferred to the CT scanner and a diagnosis of aortic dissection was made.
+
+Aortic dissection is an uncommon disorder in which a small tear occurs within the aortic wall (eFig. 3.120). The aortic wall contains three layers, an intima, a media, and an adventitia. A tear in the intima extends into the media and peels it away, forming a channel within the wall of the vessel.
+
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+
+eFig. 3.119  Chest radiograph demonstrating translucent notches along the inferior border of ribs III to VI.
+
+
+
+
+
+
+
+Usually the blood reenters the main vessel wall distal to its point of entry.
+
+The myocardial infarction
+Aortic dissection may extend retrogradely to involve the coronary sinus of the right coronary artery. Unfortunately, in this patient’s case the right coronary artery became occluded as the dissection passed into the origin. In normal individuals the right coronary artery supplies the anterior inferior aspect of the myocardium, and this is evident as an anterior myocardial infarct on an ECG.
+
+The ischemic left leg
+The two channels within the aorta have extended throughout the length of the aorta into the right iliac system and to the level of the right femoral artery. Although blood flows through these structures it often causes reduced blood
+
+
+247.e4
+Clinical Cases  •  Case 8	3
+
+
+
+Case 8—cont’d
+
+flow. Hence the reduced blood flow into the left lower limb renders it ischemic.
+
+The patient became acidotic.
+
+All cells in the body produce acid, which is excreted in the urine or converted into water with the production of carbon dioxide, which is removed with ventilation. Unfortunately, when organs become extremely ischemic they release significant amounts of hydrogen ions. Typically, this occurs when the gut becomes ischemic. With the pattern of dissection, (1) the celiac trunk, superior mesenteric artery, and inferior mesenteric artery can be effectively removed from the circulation or (2) the blood flow within these vessels can be significantly impeded, rendering the gut ischemic and hence accounting for the relatively high hydrogen ion levels.
+
+
+
+Kidney ischemia
+Similarly the dissection can impair blood flow to the kidneys, which decreases their ability to function.
+
+Treatment
+The patient underwent emergency surgery and survived. Interestingly, the height of the patient and the previous lens surgery would suggest a diagnosis of Marfan syndrome, and a series of blood tests and review of the family history revealed this was so.
+
+
+
+The true lumen surrounded	The false lumen	Collapsed intima and media by the collapsed intima and media
+
+
+
+Entry point
+
+
+
+Ascending	Thoracic aorta aorta
+
+
+
+
+Return point
+
+
+
+A
+
+The true lumen	The false lumen	B
+
+eFig. 3.120  A. CT image of aortic dissection. B. Normal aorta (left) and an aortic dissection (right). The line in the right figure indicates the plane of the CT scan shown in A.
+
+
+
+
+
+
+
+
+
+
+247.e5
+Thorax
+
+
+
+Case 9 PNEUMONIA
+A 35-year-old male patient presented to his family practitioner because of recent weight loss (14 lb over the previous 2 months). He also complained of a cough with streaks of blood in the sputum (hemoptysis) and left-sided chest pain. Recently, he noticed significant sweating, especially at night, which necessitated changing his sheets.
+
+On examination the patient had a low-grade temperature and was tachypneic (breathing fast). There was reduced expansion of the left side of the chest. When the chest was percussed it was noted that the anterior aspect of the left chest was dull, compared to the resonant percussion note of the remainder of the chest. Auscultation (listening with a stethoscope) revealed decreased breath sounds, which were hoarse in nature (bronchial breathing).
+
+A diagnosis of chest infection was made.
+
+Chest infection is a common disease. In most patients the infection affects the large airways and bronchi. If the infection continues, exudates and transudates are produced, filling the alveoli and the secondary pulmonary lobules. The diffuse patchy nature of this type of infection is termed bronchial pneumonia.
+
+Given the patient’s specific clinical findings, bronchial pneumonia was unlikely.
+
+From the clinical findings it was clear that the patient was likely to have a pneumonia confined to a lobe. Because there are only two lobes in the left lung, the likely diagnosis was a left upper lobe pneumonia.
+
+A chest radiograph was obtained (eFig. 3.121). The posteroanterior view of the chest demonstrated an area of veil-like opacification throughout the whole of the left lung.
+
+Knowing the position of the oblique fissure, any consolidation within the left upper lobe will produce this
+
+
+
+veil-like shadowing. Lateral radiographs are usually not necessary but would demonstrate opacification anteriorly and superiorly that ends abruptly at the oblique fissure.
+
+Upper lobe pneumonias are unusual because most patients develop gravity-dependent infection. Certain infections, however, are typical within the middle and upper lobes, commonly, tuberculosis (TB) and histoplasmosis.
+
+A review of the patient’s history suggested a serious and chronic illness and the patient was admitted to hospital.
+
+After admission a bronchoscopy was carried out and sputum was aspirated from the left upper lobe bronchus. This was cultured in the laboratory and also viewed under the microscope and tuberculous bacilli (TB) were identified.
+
+
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+
+
+eFig. 3.121  Chest radiograph showing left upper lobe infection.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+247.e6
+Clinical Cases  •  Case 10	3
+
+
+
+Case 10 ESOPHAGEAL CANCER
+A 68-year-old man came to his family physician complaining of discomfort when swallowing (dysphagia). The physician examined the patient and noted since his last visit he had lost approximately 18 lb over 6 months. Routine blood tests revealed the patient was anemic and he was referred to the gastroenterology unit. A diagnosis of esophageal cancer was made and the patient underwent a resection, which involved a chest and abdominal incision. After 4 years the patient remains well though still subject to follow-up.
+
+The patient underwent a flexible endoscopic examination of the esophagus in which a tube is placed through the mouth and into the esophagus and a camera is placed on the end of the tube. It is also possible to use biopsy forceps to obtain small portions of tissue for adequate diagnosis.
+
+The diagnosis of esophageal carcinoma was made (squamous cell type) and the patient underwent a staging procedure.
+
+Staging of any malignancy is important because it determines the extent of treatment and allows the physician to determine the patient’s prognosis. In this case our patient underwent a CT scan of the chest and abdomen, which revealed no significant lymph nodes around the lower third esophageal tumor.
+
+The abdominal scan revealed no evidence of spread to the nodes around the celiac trunk and no evidence of spread to the liver.
+
+Bleeding was the cause of the anemia.
+
+Many tumors of the gastrointestinal system are remarkably friable, and with the passage of digested material across the tumor, low-grade chronic bleeding occurs. Over a period of time the patient is rendered anemic, which in the first instance is asymptomatic; however, it can be diagnosed on routine blood tests.
+
+
+
+Complex surgery is planned.
+
+The length of the esophagus is approximately 22 cm. Tumor spread can occur through the submucosal route and also through locoregional lymph nodes. The lymph nodes drain along the arterial supply to the esophagus, which is predominantly supplied by the inferior thyroid artery, esophageal branches from the thoracic aorta, and branches from the left gastric artery. The transthoracic esophagectomy procedure involves placing the patient supine. A laparotomy is performed to assess for any evidence of disease in the abdominal cavity. The stomach is mobilized, with preservation of the right gastric and right gastro-omental arteries. The short gastric vessels and left gastric vessels are divided, and a pyloromyotomy is also performed.
+
+The abdominal wound is then closed and the patient is placed in the left lateral position. A right posterolateral thoracotomy is performed through the fifth intercostal space, and the azygos vein is divided to provide full access to the whole length of the esophagus. The stomach is delivered through the diaphragmatic hiatus. The esophagus is resected and the stomach is anastomosed to the cervical esophagus.
+
+The patient made an uneventful recovery.
+
+Most esophageal cancers are diagnosed relatively late and often have lymph node metastatic spread. A number of patients will also have a spread of tumor to the liver. The overall prognosis for esophageal cancer is poor, with approximately a 25%, 5-year survival rate.
+
+Diagnosing esophageal cancer in its early stages before lymph node spread is ideal and can produce a curative procedure.
+
+Our patient went on to have chemotherapy and enjoys a good quality of life 4 years after his operation.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+247.e7
+Thorax
+
+
+
+Case 11 VENOUS ACCESS
+A 45-year-old woman, with a history of breast cancer in the left breast, returned to her physician. Unfortunately the disease had spread to the axillary lymph nodes and bones (bony metastatic disease). A surgeon duly resected the primary breast tumor with a wide local excision and then performed an axillary nodal clearance. The patient was then referred to an oncologist for chemotherapy. Chemotherapy was delivered through a portacath, which is a subcutaneous reservoir from which a small catheter passes under the skin into the internal jugular vein. The patient duly underwent a portacath insertion without
+complication, completed her course of chemotherapy, and is currently doing well 5 years later.
+
+The portacath was placed on the patient’s right anterior chest wall and the line was placed into the right internal jugular vein. The left internal jugular vein and subcutaneous tissues were not used. The reason for not using this site was that the patient had previously undergone an axillary dissection on the left, and the lymph nodes and lymphatics were removed. Placement of a portacath in this region may produce an inflammatory response and may even get infected. Unfortunately, because there are no lymphatics to drain away infected material and to remove bacteria, severe sepsis and life-threatening infection may ensue.
+
+How was it placed?
+
+The ultrasound shows an axial image across the root of the neck on the right demonstrating the right common carotid
+
+
+
+artery and the right internal jugular vein. The internal jugular vein is the larger of the two structures and generally demonstrates normal respiratory variation, compressibility, and a size dependence upon the patient’s position (when the patient is placed in the head-down position, the vein fills and makes puncture easy).
+
+The risks of the procedure
+As with all procedures and operations there is always a small risk of complication. These risks are always balanced against the potential benefits of the procedure. Placing the needle into the internal jugular vein can be performed under ultrasound guidance, which reduces the risk of puncturing the common carotid artery. Furthermore, by puncturing under direct vision it is less likely that the operator will hit the lung apex and pierce the superior pleural fascia, which may produce a pneumothorax.
+
+The position of the indwelling catheter
+The catheter is placed through the right internal jugular vein and into the right brachiocephalic vein. The tip of the catheter is then placed more inferiorly at the junction of the right atrium and the superior vena cava. The reason for placing the catheter in such a position relates to the agents that are infused. Most chemotherapeutic agents are severely cytotoxic (kill cells), and enabling good mixing with the blood prevents thrombosis and vein wall irritation.
+
+
+
+
+
+Case 12
+
+CYSTIC FIBROSIS WITH BRONCHIECTASIS
+
+A 15-year-old girl presented to the emergency department with a 1-week history of productive cough with copious purulent sputum, increasing shortness of breath, fatigue, fever around 38.5°C, and no response to oral amoxicillin prescribed to her by a family physician. The patient was diagnosed with cystic fibrosis shortly after birth and had multiple admissions to the hospital for pulmonary and gastrointestinal manifestations of the disease.
+
+Physical examination on the current admission to the ER revealed widespread inspiratory crackles, mild tachycardia of 105/min, and fever of 38.2°C. Diagnosis of infective exacerbation of bronchiectasis was made. Sputum was sent for microbiology, which later came back positive for Pseudomonas aeruginosa, a common pathogen isolated in such patients.
+
+Cystic fibrosis is an autosomal recessive disorder affecting
+247.e8	the function of exocrine glands due to a gene mutation, leading to an abnormally low concentration of chloride in
+
+
+
+exocrine secretions, rendering them thick and sticky. Thick secretions cause blockage and subsequent damage to the airways, bowel, pancreas, liver, and reproductive tract. In the lungs, thick nonclearing secretions lead to recurrent infections and persistent inflammation, resulting in permanent distortion and dilation of the distal bronchi, a condition known as bronchiectasis. Bronchiectasis can be seen on plain chest radiographs as tubular (tram track like) structures, particularly affecting the upper lobes. Computed tomography can easily demonstrate the extent of airway damage and identify potential pulmonary complications of cystic fibrosis such as lobar collapse, pneumothorax, or enlargement of the pulmonary trunk due to pulmonary hypertension.
+
+The patient was admitted for a course of broad-spectrum intravenous antibiotics and intensive chest physiotherapy and made satisfactory recovery from the acute episode. She was discharged home on oral prophylactic antibiotics with an ongoing physiotherapy program.
+This page intentionally left blank
+Conceptual Overview  •  General Description	4
+
+
+Conceptual overview GENERAL DESCRIPTION
+
+
+The abdomen is a roughly cylindrical chamber extending from the inferior margin of  the thorax to the superior margin of the pelvis and the lower limb (Fig. 4.1A).
+The inferior thoracic aperture forms the superior opening to the abdomen and is closed by the diaphragm. Inferiorly, the deep abdominal wall is continuous with the
+
+pelvic wall at the pelvic inlet. Superficially, the inferior limit of the abdominal wall is the superior margin of the lower limb.
+The chamber enclosed by the abdominal wall contains a single large peritoneal cavity, which freely communi-cates with the pelvic cavity.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Diaphragm
+
+
+
+Inferior thoracic aperture
+
+
+
+
+
+Abdominal wall
+
+
+Iliac crest	Pelvic inlet
+
+
+
+Lower limb
+
+
+Inguinal ligament
+
+
+
+
+
+A
+
+Fig. 4.1  Abdomen. A. Boundaries.	251
+Abdomen
+
+
+
+
+
+
+
+
+
+
+Costal margin
+
+
+
+Gastrointestinal tract
+
+
+
+
+
+Peritoneal  cavity
+
+
+
+
+
+Mesentery
+
+
+
+Right kidney
+
+B
+
+Left kidney
+
+
+
+
+
+
+Muscles
+
+
+Aorta
+
+
+Inferior vena cava
+
+
+Fig. 4.1, cont’d  B. Arrangement of abdominal contents. Inferior view.
+
+
+
+
+
+
+Abdominal viscera are either suspended in the perito-neal cavity by mesenteries or positioned between the cavity and the musculoskeletal wall (Fig. 4.1B).
+Abdominal viscera include:
+
+
+FUNCTIONS
+Houses and protects major viscera
+The abdomen houses major elements of the gastrointestinal system (Fig. 4.2), the spleen, and parts of  the urinary
+
+
+
+■     major  elements  of  the  gastrointestinal  system—the caudal end of the esophagus, stomach, small and large intestines, liver, pancreas, and gallbladder;
+■     the spleen;
+
+system.
+Much of the liver, gallbladder, stomach, and spleen and parts of the colon are under the domes of the diaphragm, which project superiorly above the costal margin of  the
+
+
+
+■     components   of   the   urinary   system—kidneys   and ureters;
+
+thoracic wall, and as a result these abdominal viscera are protected by the thoracic wall. The superior poles of the
+
+
+
+■     the suprarenal glands; and
+■     major neurovascular structures.
+
+kidneys are deep to the lower ribs.
+Viscera not under the domes of the diaphragm are sup-ported and protected predominantly by the muscular walls of the abdomen.
+
+
+
+
+252
+Conceptual Overview  •  Functions	4
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Rib cage
+
+
+
+
+Costal margin	Spleen
+
+Liver
+Stomach
+
+
+
+
+
+
+
+
+Colon
+Small intestine
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 4.2  The abdomen contains and protects the abdominal viscera.
+
+
+
+
+
+
+
+
+253
+Abdomen
+
+
+
+
+
+
+
+
+
+
+Diaphragm
+
+
+Contraction of diaphragm
+
+Relaxation of abdominal muscles
+
+
+Relaxation of diaphragm
+
+
+
+Contraction of abdominal muscles
+
+
+
+
+
+
+
+
+
+
+
+Inspiration	Expiration
+
+Fig. 4.3  The abdomen assists in breathing.
+
+
+
+
+
+
+Breathing
+One of the most important roles of the abdominal wall is to assist in breathing:
+
+
+Laryngeal cavity closed
+
+Air retained in thorax
+
+
+
+■     It relaxes during inspiration to accommodate expansion of the thoracic cavity and the inferior displacement of abdominal viscera during contraction of the diaphragm (Fig. 4.3).
+■     During expiration, it contracts to assist in elevating the domes of  the diaphragm, thus reducing thoracic volume.
+
+Material can be expelled from the airway by forced
+
+
+Fixed diaphragm
+
+Contraction of abdominal wall
+Increase in intraabdominal pressure
+
+Micturition
+Child birth	Defecation
+
+
+
+expiration using the abdominal muscles, as in coughing or sneezing.
+
+
+Changes in intraabdominal pressure
+Contraction of abdominal wall muscles can dramatically 254	increase intraabdominal pressure when the diaphragm is
+
+
+Fig. 4.4  Increasing intraabdominal pressure to assist in micturition, defecation, and childbirth.
+
+
+in a fixed position (Fig. 4.4). Air is retained in the lungs by closing valves in the larynx in the neck. Increased intra-abdominal pressure assists in voiding the contents of the bladder and rectum and in giving birth.
+Conceptual Overview  •  Component Parts	4
+
+
+
+COMPONENT PARTS
+Wall
+
+Muscles  make  up  the  rest  of   the  abdominal  wall (Fig. 4.5B):
+
+
+
+The abdominal wall consists partly of  bone but mainly of  muscle (Fig. 4.5). The skeletal elements of  the wall (Fig. 4.5A) are:
+
+■     Lateral to the vertebral column, the quadratus lumbo-rum, psoas major, and iliacus muscles reinforce the posterior aspect of the wall. The distal ends of the psoas major and iliacus muscles pass into the thigh and are
+
+
+
+■     the five lumbar vertebrae and their intervening inter-vertebral discs,
+■     the superior expanded parts of the pelvic bones, and
+■     bony components of the inferior thoracic wall, includ-ing the costal margin, rib XII, the end of rib XI, and the xiphoid process.
+
+major flexors of the hip joint.
+■     Lateral parts of the abdominal wall are predominantly formed by three layers of muscles, which are similar in orientation to the intercostal muscles of the thorax— transversus abdominis, internal oblique, and external oblique.
+
+
+
+
+
+
+
+
+
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+
+Rib XII
+
+Iliolumbar ligament
+
+
+External oblique
+
+Costal margin
+
+Internal oblique
+
+Transversus abdominis
+
+Quadratus lumborum
+
+
+Rectus abdominis
+
+
+
+
+Pelvic inlet
+
+
+
+
+Inguinal ligament                       Gap between inguinal ligament and pelvic bone
+
+
+Iliacus
+
+Psoas major
+
+
+
+A	B
+
+Fig. 4.5  Abdominal wall. A. Skeletal elements. B. Muscles.	255
+Abdomen
+
+
+
+■     Anteriorly, a segmented muscle (the rectus abdominis) on each side spans the distance between the inferior thoracic wall and the pelvis.
+
+Structural continuity between posterior, lateral, and
+
+
+Branch of aorta
+
+Gastrointestinal tract
+
+Ventral mesentery
+
+
+Aorta
+
+Kidney—posterior to peritoneum
+
+anterior  parts  of   the  abdominal  wall  is  provided  by thick  fascia  posteriorly  and  by  flat  tendinous  sheets (aponeuroses) derived from muscles of the lateral wall. A fascial layer of varying thickness separates the abdominal wall  from  the  peritoneum,  which  lines  the  abdominal cavity.
+
+
+Abdominal cavity
+The general organization of the abdominal cavity is one in which a central gut tube (gastrointestinal system) is suspended from the posterior abdominal wall and partly from the anterior abdominal wall by thin sheets of tissue (mesenteries; Fig. 4.6):
+
+■     a ventral (anterior) mesentery for proximal regions of the gut tube;
+■     a dorsal (posterior) mesentery along the entire length of the system.
+
+
+Different parts of  these two mesenteries are named according to the organs they suspend or with which they are associated.
+Major viscera, such as the kidneys, that are not sus-pended in the abdominal cavity by mesenteries are associ-ated with the abdominal wall.
+
+
+
+Dorsal mesentery
+
+Parietal peritoneum
+
+Visceral peritoneum
+
+
+
+The abdominal cavity is lined by peritoneum, which consists of an epithelial-like single layer of cells (the meso-
+
+
+Fig. 4.6  The gut tube is suspended by mesenteries.
+
+
+
+thelium) together with a supportive layer of connective tissue.  Peritoneum  is  similar  to  the  pleura  and  serous pericardium in the thorax.
+The  peritoneum  reflects  off  the  abdominal  wall  to become a component of the mesenteries that suspend the viscera.
+
+■     Parietal peritoneum lines the abdominal wall. ■     Visceral peritoneum covers suspended organs.
+
+
+■     Intraperitoneal structures, such as elements of  the gastrointestinal system, are suspended from the abdomi-nal wall by mesenteries;
+■     Structures that are not suspended in the abdominal cavity by a mesentery and that lie between the parietal peritoneum and abdominal wall are retroperitoneal in position.
+
+Retroperitoneal  structures  include  the  kidneys  and
+
+Normally, elements of  the gastrointestinal tract and	ureters, which develop in the region between the perito-its   derivatives   completely   fill   the   abdominal   cavity,	neum and the abdominal wall and remain in this position
+
+making  the  peritoneal  cavity  a  potential  space,  and visceral peritoneum on organs and parietal peritoneum on the adjacent abdominal wall slide freely against one another.
+
+in the adult.
+During development, some organs, such as parts of the small and large intestines, are suspended initially in the abdominal cavity by a mesentery, and later become retro-
+
+Abdominal   viscera   are   either   intraperitoneal   or	peritoneal secondarily by fusing with the abdominal wall retroperitoneal:	(Fig. 4.7).
+256
+Conceptual Overview  •  Component Parts	4
+
+
+Visceral peritoneum
+
+Gastrointestinal tract
+
+
+
+Artery to gastrointestinal tract
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Mesentery
+
+A
+
+
+Retroperitoneal structures
+Parietal peritoneum
+
+
+
+Intraperitoneal part of gastrointestinal tract
+
+
+
+
+Gastrointestinal tract
+
+B	Mesentery before fusion with wall
+
+
+
+Secondary retroperitoneal part of gastrointestinal tract
+
+
+
+
+Gastrointestinal tract
+
+
+
+
+
+
\ No newline at end of file