Thoracic Wall Anatomy PDF

Thoracic Wall & the Breast 1 Overview ▪ The thorax is the superior part of the trunk between the neck and abdomen. ▪ The thoracic cavity, surrounded by the thoracic wall, contains the heart, lungs, thymus, distal part of the trachea, and most of the esophagus. ▪ The...

Thoracic Wall & the Breast 1 Overview ▪ The thorax is the superior part of the trunk between the neck and abdomen. ▪ The thoracic cavity, surrounded by the thoracic wall, contains the heart, lungs, thymus, distal part of the trachea, and most of the esophagus. ▪ The thoracic cavity is divided into three compartments: the central mediastinum, occupied by the heart and structures transporting air, blood, and food; and the right and left pulmonary cavities, occupied by the lungs. ▪ To perform a physical examination of the thorax, a working knowledge of its structure and vital organs is required. 2 ❑ SUPERIOR THORACIC APERTURE Boundaries ▪ Posteriorly, by vertebra T1, the body of which protrudes anteriorly into the opening. ▪ Laterally, by the 1st pair of ribs and their costal cartilages. ▪ Anteriorly, by the superior border of the manubrium. ❑ INFERIOR THORACIC APERTURE Boundaries ▪ Posteriorly, by the 12th thoracic vertebra, the body of which protrudes anteriorly into the opening. ▪ Posterolaterally, by the 11th and 12th pairs of ribs. ▪ Anterolaterally, by the joined costal cartilages of ribs 7–10, forming the costal margins. ▪ Anteriorly, by the xiphisternal joint. 3 Bones of the Thoracic Wall The bones of the thoracic wall consist of the sternum, the ribs, and the costal cartilages 4 STERNUM The sternum is a flat bone that is divided into three parts: the manubrium, the body, and the xiphoid process. Manubrium Forms the upper part of the sternum. It articulates with the body of the sternum at the manubriosternal joint. It articulates with the clavicles and with the first costal cartilage and the upper part of the second costal cartilage on each side. The jugular (suprasternal) notch on the superior aspect of the manubrium 5 The sternal angle (angle of Louis) ❑ It is formed by the articulation of the manubrium with the body of the sternum. ❑ It is an important surface landmark, and it lies at the level of: 1. The second costal cartilage. 2. The intervertebral disc between the fourth and fifth thoracic vertebrae. 3. The junction of the ascending aorta and the aortic arch and the junction of the aortic arch and the descending thoracic aorta. 4. The bifurcation of the trachea. 5. The junction of the superior mediastinum and the inferior mediastinum 6 Body of the Sternum The body of the sternum articulates above with the manubrium at the manubriosternal joint and below with the xiphoid process at the xiphisternal joint. On each side, it articulates with the second to the seventh costal cartilages Xiphoid Process The xiphoid process is a thin plate of cartilage that becomes ossified at its proximal end during adult life. STERNUM AND MARROW BIOPSY Because the sternum possesses red hemopoietic marrow throughout life, the body of the sternum is a common site for marrow biopsy. 7 RIBS There are twelve pairs of ribs, all of which are attached posteriorly to the thoracic vertebrae. Ribs are divided into three categories: ▪ True ribs: The upper seven pairs are attached to the sternum by their costal cartilages. ▪ False ribs: The eighth, ninth, and tenth pairs are attached anteriorly to each other and to the seventh rib by their costal cartilages and small synovial joints. ▪ Floating ribs: The eleventh and twelfth pairs have no anterior attachment. Floating are also false 8 Typical Rib (3rd–9th) The typical rib is a long, twisted flat bone with a rounded superior border and a grooved inferior border (the costal groove), which accommodates the intercostal vessels and nerve. The anterior end of each rib is attached to the corresponding costal cartilage. A rib has a head, neck, tubercle, shaft, and angle. The head has two facets for articulation with the numerically corresponding vertebral body and the vertebra immediately above it. The tubercle has a facet for articulation with the transverse process of the numerically corresponding vertebra. The angle is where the shaft bends forward sharply. 9 10 Atypical Rib The first rib is important clinically because of its close relationship to the nerves of the brachial plexus and the subclavian artery and vein. The rib is small and flattened from above downward. The scalenus anterior is attached to its upper surface and inner border. Anterior to the scalenus anterior, the subclavian vein crosses the rib. posterior to the muscle attachment, the subclavian artery and lower trunk of the brachial plexus lie in contact with the bone. 11 The 2nd rib Has a thinner, less curved body and is substantially longer than the 1st rib. Its head has two facets for articulation with the bodies of the T1 and T2 vertebrae; Its main atypical feature is a rough area on its upper surface, the tuberosity for serratus anterior, from which part of that muscle originates. 12 ▪ The 10th–12th ribs, like the 1st rib, have only one facet on their heads and articulate with a single vertebra. ▪ The 11th and 12th ribs are short and have no neck or tubercle. 13 COSTAL CARTILAGES ▪ The costal cartilages are bars of cartilage connecting the upper seven ribs to the lateral edge of the sternum and the eighth, ninth, and tenth ribs to the cartilage immediately above them. ▪ The cartilages of the eleventh and twelfth ribs end in the abdominal musculature. 14 Joints of the Thoracic Wall 1. MANUBRIOSTERNAL JOINT ▪ It is a cartilaginous joint. ▪ The bony surfaces are covered with hyaline cartilage and joined by a disc of fibrocartilage. ▪ A small amount of movement is possible during respiration. 2. XIPHISTERNAL JOINT The xiphisternal joint is a cartilaginous joint. The xiphoid process usually fuses with the body of the sternum during middle age. 15 3. COSTOVERTEBRAL J OINTS From the second to the ninth ribs. The head articulates by a synovial joint with the corresponding vertebral body and that of the vertebra above it. There is a strong intra-articular ligament that connects the head to the intervertebral disc. The heads of the first and the lowest three ribs have a simple synovial joint with the corresponding vertebral body. The tubercle of a rib articulates by a synovial joint with the transverse process of the corresponding vertebra. (This joint is absent on the eleventh and twelfth ribs.) 16 4. COSTOCHONDRAL JOINTS Costochondral joints are cartilaginous joints. No movement is possible. 5. JOINTS OF THE COSTAL CARTILAGES WITH THE STERNUM The first costal cartilages articulate with the manubrium by cartilaginous joints that permit no movement. The second to the seventh costal cartilages articulate with the lateral border of the sternum by synovial joints. The sixth, seventh, eighth, ninth, and tenth costal cartilages articulate with one another along their borders by small synovial joints. The cartilages of the eleventh and twelfth ribs are embedded in the abdominal musculature. 17 18 Muscles of the Thoracic Wall The muscles of the thoracic wall are summarized in the following Table 19 20 INTERCOSTAL SPACES The spaces between the ribs contain three muscles of respiration: The external intercostal, the internal intercostal, and the innermost intercostal muscle. The intercostal nerves and blood vessels RUN between the internal and the innermost intercostal muscles. They are arranged in the following order from above downward: intercostal vein, intercostal artery, and intercostal nerve (i.e., VAN). 21 DIAPHRAGM The diaphragm is the most important muscle of respiration. It is dome shaped, and it consists of a peripheral muscular part and a centrally placed tendon. The origin of the diaphragm is divided into three parts: 1. A sternal part arising from the posterior surface of the xiphoid process. 2. A costal part arising from the deep surfaces of the lower six ribs and their costal cartilages. 3. A vertebral part arising from vertical columns or crura and from the arcuate ligaments. 22 ▪ The right crus arises from the sides of the bodies of the first three lumbar vertebrae and the intervertebral discs, and it splits to enclose the esophagus. ▪ The left crus arises from the sides of the bodies of the first two lumbar vertebrae and the intervertebral disc. As seen from the front, the diaphragm curves up into right and left domes. These domes support the right and left lungs, whereas the central tendon supports the heart. 23 Openings in the Diaphragm ▪ Aortic Opening Lies anterior to the body of the twelfth thoracic vertebra between the crura and transmits the aorta, the thoracic duct, and the azygos vein. ▪ Esophageal Opening Lies at the level of the tenth thoracic vertebra in a sling of muscle fibers derived from the right crus. It transmits the esophagus, the right and left vagus nerves, the esophageal branches of the left gastric vessels, and the lymphatic vessels from the lower third of the esophagus. ▪ Caval Opening Lies at the level of the eighth thoracic vertebra in the central tendon. It transmits the inferior vena cava and the terminal branches of the right phrenic nerve. 24 Blood Vessels of the Thoracic Wall ❑ INTERCOSTAL ARTERIES AND VEINS Each intercostal space possesses a large, single posterior intercostal artery and two small anterior intercostal arteries. The corresponding posterior intercostal veins drain into the azygos or hemiazygos veins. The corresponding anterior intercostal veins drain into the internal thoracic and musculophrenic veins. ❑ Posterior Intercostal Arteries The posterior intercostal arteries of the first two spaces are branches of the superior intercostal artery, which in turn is a branch of the costocervical trunk of the subclavian artery. The posterior intercostal arteries of the lower nine spaces are branches of the thoracic aorta. 25 ❑ Anterior Intercostal Arteries The anterior intercostal arteries of the first six spaces are branches of the internal thoracic artery. The anterior intercostal arteries of the lower spaces are branches of the musculophrenic artery (one of the terminal branches of the internal thoracic artery). 26 ❑ INTERNAL THORACIC ARTERY AND VEIN Internal Thoracic Artery The internal thoracic artery arises from the first part of the subclavian artery. It descends directly behind the first six costal cartilages and in front of the parietal pleura, and it lies about a fingerbreadth lateral to the sternum. It terminates in the sixth intercostal space by dividing into the superior epigastric artery and the musculophrenic arteries. Branches Anterior intercostal arteries supply the upper six intercostal spaces. Perforating arteries pierce the intercostal muscles and supply the skin and the mammary gland. Pericardiophrenic artery supplies the pericardium and the diaphragm. Mediastinal arteries supply the mediastinum, including the thymus. Superior epigastric artery enters the rectus sheath and supplies the upper part of the rectus muscle. Musculophrenic artery follows the costal margin on the upper surface of the diaphragm and supplies the diaphragm and the lower intercostal spaces. 27 ❑ Internal Thoracic Vein The internal thoracic vein begins as venae comitantes of the internal thoracic artery. The venae eventually join to form a single vessel that drains into the brachiocephalic vein on each side. 28 Lymphatic Drainage of the Thoracic Wall The skin of the anterior chest wall drains to the anterior axillary lymph nodes. The skin of the posterior chest wall drains to the posterior axillary nodes. The intercostal spaces drain forward to the internal thoracic nodes, which are situated along the internal thoracic artery, and posteriorly to the posterior intercostal nodes, which is close to the heads of the ribs and the paraaortic nodes in the posterior mediastinum. 29 Nerves of the Thoracic Wall INTERCOSTAL NERVES The intercostal nerves are the anterior rami of the first eleven thoracic spinal nerves. Each nerve enters an intercostal space and runs forward inferiorly to the intercostal vessels in the subcostal groove of the corresponding rib, between the innermost and the internal intercostal muscles. The first six nerves are distributed within their intercostal spaces. The seventh, eighth, and ninth intercostal nerves leave the anterior ends of their intercostal spaces by passing deep to the costal cartilages to enter the abdominal wall. The tenth and eleventh nerves pass forward directly into the abdominal wall. 30  INTERCOSTAL NERVES Branches Collateral branch runs forward below the main nerve. Lateral cutaneous branch divides into anterior and posterior branches that supply the skin. Anterior cutaneous branch Muscular branches run to the intercostal muscles. Pleural branches run to the parietal pleura, and peritoneal branches ( seventh to eleventh intercostal nerves only) run to the parietal peritoneum. CORONARY HEART DISEASE AND THE INTERCOSTOBRACHIAL NERVE In coronary heart disease pain is often referred along the intercostobrachial nerve to the medial side of the arm. 31 Breasts The breasts are the most prominent superficial structures in the anterior thoracic wall, especially in women. The breasts (L. mammae) consist of glandular and supporting fibrous tissue embedded within a fatty matrix, together with blood vessels, lymphatics, and nerves. Both men and women have breasts; normally, they are well developed only in women. The mammary glands are in the subcutaneous tissue overlying the pectoralis major and minor muscles. At the greatest prominence of the breast is the nipple, surrounded by a circular pigmented area of skin, the areola (L. small area). 32 Location of the breast ❑ The base of the female breast extends transversely from the lateral border of the sternum to the midaxillary line. ❑ vertically from the second to sixth ribs. ❑ A small part of the breast may extend along the inferolateral edge of the pectoralis major muscle toward the axillary fossa, forming an axillary process or tail (of Spence). Two thirds of the breast rests on the pectoral fascia covering the pectoralis major; one third rests on the fascia covering the serratus anterior muscle 33 34 Retromammary space (bursa): is the space between the breast and the deep pectoral fascia , filled by loose connective tissue and contains a small amount of fat, allows the breast some degree of movement on the deep pectoral fascia. Suspensory ligaments (of Cooper): Attach the mammary glands to the dermis. 35 Structure of the breast ▪ Nipple, surrounded by a circular pigmented area (the areola ). ▪ Contains 15 to 20 lobules of glandular tissue, which constitute the parenchyma of the mammary gland. ▪ Each lobule is drained by a lactiferous duct , which opens independently on the nipple. ▪ Just deep to the areola, each duct has a dilated portion, the lactiferous sinus. 36 Breast Quadrants ▪ For the anatomical location and description of pathology (e.g., cysts and tumors), the breast is divided into four quadrants. ▪ The axillary tail is an extension of the mammary gland of the superolateral quadrant 37 VASCULATURE OF BREAST The arterial supply of the breast is derived from: 1. Medial mammary branches of perforating branches and anterior intercostal branches of the internal thoracic artery, originating from the subclavian artery. 2. Lateral thoracic and thoraco-acromial arteries, branches of the axillary artery 3. Posterior intercostal arteries, branches of the thoracic aorta in the intercostal spaces 38 The venous drainage of the breast is mainly to the axillary vein, but there is some drainage to the internal thoracic vein. 39 The lymphatic drainage of the breast ▪ It is important because of its role in the metastasis (spread) of cancer cells. ▪ Lymph passes from the nipple, areola, and lobules of the gland to the subareolar lymphatic plexus, and from it: ❖ Most lymph (>75%), especially from the lateral quadrants of the breasts, drains to the axillary lymph nodes (pectoral, humeral, subscapular, central, and apical). ▪ Most of the lymph first drains to the pectoral (anterior) nodes. However, some lymph may drain directly to other axillary nodes, or to interpectoral, deltopectoral, supraclavicular, or inferior deep cervical nodes. 40  The lymphatic drainage of the breast ❖ Lymph from the medial breast quadrants drains to the parasternal lymph nodes or to the opposite breast. C. ❖ Lymph from the inferior breast quadrants may pass deeply to abdominal lymph nodes (inferior phrenic nodes). 41 ❖ Lymph from the axillary nodes drains to infraclavicular and supraclavicular nodes and from them to the subclavian lymphatic trunk. ❖ Lymph from the parasternal nodes enters the bronchomediastinal trunks, which ultimately drain into the thoracic or right lymphatic duct 42 NERVES OF BREAST The nerves of the breasts derive from the anterior and lateral cutaneous branches of the fourth to sixth intercostal nerves 43 Carcinoma of Breast Carcinomas of the breast are malignant tumors, usually adenocarcinomas arising from the epithelial cells of the lactiferous ducts Breast cancer can spread via lymphatics (lymphogenic metastasis) and veins. lymphedema (edema, excess fluid in the subcutaneous tissue), which in turn may result in deviation of the nipple and a thickened, leatherlike appearance of the skin Prominent or “puffy” skin between dimpled pores gives it orange-peel appearance an orange-peel appearance (peau d'orange sign) 44 Thank you ! 45