Pectoral Region Anatomy PDF

# **PECTORAL REGION** ## **PROF. SC GBOTOLORUN** # **THE PECTORAL REGION** * The pectoral region is located on the anterior chest wall. * It contains 4 muscles that move the pectoral girdle: * Pectoralis major * Pectoralis minor * Subclavius * Serratus anterior # **PECTORALIS MAJOR...

# **PECTORAL REGION** ## **PROF. SC GBOTOLORUN** # **THE PECTORAL REGION** * The pectoral region is located on the anterior chest wall. * It contains 4 muscles that move the pectoral girdle: * Pectoralis major * Pectoralis minor * Subclavius * Serratus anterior # **PECTORALIS MAJOR** * is the superior most and largest muscle of the anterior chest wall * It is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla * It has clavicular and sternocostal heads * Its inferior border forms the anterior axillary fold * Together with the deltoid, they form the deltopectoral triangle. # **PECTORALIS MINOR** * Lies in the anterior chest wall where it is almost completely covered by the larger pectoralis major muscle * It is triangular in shape * Its base is formed by fleshy slips attached to the anterior ends of the 3rd-5th ribs near their coastal cartilages * Its apex is on the coracoid process of the scapula * It is a useful anatomical and surgical landmark for structures in the axilla (e.g., axillary artery) * It creates a passage for vessels, nerves, and the lateral thoracic artery. # **PECTORALIS MINOR IN RELATION TO VESSELS AND NERVES** # **SUBCLAVIUS** * Lies almost horizontally when the arm is in the anatomical position * The subclavius is a small, triangular muscle in the chest that stabilizes the clavicle * It is located between the first rib and the clavicle, and is part of the anterior chest wall. * It affords some protection to the subclavian vessels and the superior trunk of the brachial plexus during fractures of the clavicle * It also helps resist the tendency for **the clavicle to dislocate at the sternoclavicular joint (e.g., when** # **SERRATUS ANTERIOR** * It was named because of the sawtoothed appearance of its fleshy slips or digitations (L. serratus, a saw) * It is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth ribs at the lateral wall of the thorax * Inserts along the whole length of the anterior surface of the medial border of the scapula, including the inferior angle * The serratus anterior holds the scapula against the thoracic wall when doing push-ups or when # **PECTORAL MUSCLES** | Muscle | Proximal Attachment | Distal Attachment | Innervation | Main Action | |---|---|---|---|---| | Pectoralis major | Clavicular head: anterior surface of medial head of clavicle<br>Sternocostal head: anterior surface of sternum, superior six costal cartilages, and aponeurosis of external oblique muscle | Lateral lip of intertubercular sulcus of humerus | Lateral and medial pectoral nerves | Adducts and medially rotates humerus; draws scapula anteriorly and inferiorly.<br>Clavicular head flexes humerus<br>Sternocostal head extends it from its flexed position | | Pectoralis minor | 3rd to 5th ribs near their costal cartilages | Medial border and superior surface of coracoid process of scapula | Medial pectoral nerve | Stabilizes scapular by drawing it inferiorly and anteriorly against thoracic wall | | Subclavius | Junction of 1st rib and its costal cartilage | Inferior surface of middle third of clavicle | Nerve to subclavius | Anchors and depresses clavicle | | Serratus anterior | External surfaces of lateral parts of 1st-8th ribs | Anterior surface of medial border of scapula | Long thoracic nerve | Protracts scapula and holds it against thoracic wall | # **THE BREASTS** # **BREASTS** * Most prominent superficial structure in anterior thoracic wall * The breast (L. mammae) consist of glandular and supporting fibrous tissue embedded within a fatty matrix, together with blood vessels, lymphatics, and nerves * Well developed only in females * At the greatest prominence of the breast is the nipple # **THE MAMMARY GLANDS** * Are in the subcutaneous tissue overlying the pectoralis major and minor muscles * The mammary glands within the breasts are accessory to reproduction in women * They are rudimentary and functionless in men where they consist of only a few small ducts or epithelial cords * Usually, the fat present in male breasts is not different from that of subcutaneous tissue elsewhere * The glandular system in males rarely develops * In the female breast, the amount of fat surrounding the glandular tissue # **THE FEMALE BREASTS** * The roughly circular body of the female breast rests on a bed of the breast that extends: * Transversely * From lateral border of sternum to midaxillary line * Vertically * From 2nd to 6th ribs * Axillary tail of Spence (axillary process) * Small part extend along inferolateral edge of # **Extent** * 2/3- rest on deep pectoral fascia overlying pectoralis major * 1/3- rests on fascia covering serratus anterior muscle * Between the breast and pectoral fascial is the retromammary # **RETROMAMMARY SPACE** * Is a loose subcutaneous tissue plane or Potential space * Contains small amount of fat * Allows breast move over pectoral fascia # **SUSPENSORY LIGAMENTS OF COOPER** * The mammary gland attached firmly to dermis of overlying skin by skin ligaments - the suspensory ligament of Cooper * Fibrous condensation of connective tissue stroma * Well developed in the superior part of the gland * Help support the lobes and lobules of the mammary gland * During puberty (8-15 years) female breasts normally enlarge primarily from increased fat deposition and secondarily from glandular # **THE GLANDULAR TISSUE OF THE BREAST** * The lactiferous ducts give rise to buds that develops * 15 to 20 lobules of the mammary gland which constitutes the parenchyma * Each lobule is drained by a lactiferous duct * opens independently on the nipple * The ducts converge towards the nipple * spokes of a bicycle wheel * Deep to the areola each duct dilates # **THE AREOLAE** * The areolae contains numerous sebaceous glands that enlarge during pregnancy * They secrete an oily substance that provides a protective lubricant for the areola and nipple # **THE NIPPLES** * Are conical/cylindrical prominences in the centre of the areolae * Devoid of fat, hair and sweat glands * The tips of the nipples are fissured with the lactiferous ducts opening into them * The nipples are composed mostly of circularly arranged smooth muscle fibers that compress the lactiferous ducts during lactation * In young nulliparous woman usually in 4th intercostal space # **BLOOD SUPPLY** * Arterial supply * Internal thoracic artery * Lateral thoracic artery * Thoracoacromial artery * Posterior intercostal arteries * Venous return * *Axillary vein* * Internal thoracic vein * Intercostal vein # **LYMPHATIC DRAINAGE** * Very important= role in metastasis of cancer cells * Lymph from nipple, areola and lobule of gland- Subareolar lymphatic plexus * Most lymph > 75% especially from lateral quadrants of breast'n Axillary nodes through pectoral nodes * Some drains directly to the deltopectoral/supraclavicular/interpectoral/inferior deep # **LYMPHATIC DRAINAGE CONT'D** * Remaining lymph particularly from medial quadrants 'n parasternal nodes/opposite breast * Lymph from lower quadrants 'n inferior phrenic (abdominal) nodes * Lymph from skin of breast 'n axillary/inferior deep cervical/infraclavicular/parasternal nodes of both sides * Lymph from axillary nodes'n infraclavicular and supraclavicular'n subclavian lymphatic trunk (drains lymph from upper limbs) * Lymph from parasternal nodes'n bronchomediastinal trunk (drains lymph from thoracic viscera) # **NERVES OF THE BREAST** * Anterior and lateral cutaneous branches of the 4th to 6th intercostal nerves # **CLINICAL ANATOMY** * Breast quadrants * Carcinoma of breast * Mastectomy/radical mastectomy/current practice lympectomy (tumor & surrounding tissues) * Gynecomastia * Polymastia, polythelia and amastia * Mamography # **MAMMOGRAM SHOWING THE 4 TYPES OF BREASTS** * Image of a mammogram showing 4 types of breasts: fatty, scattered fibroglandular densities, heterogeneously dense, and extremely dense. # **MAMMOGRAM SHOWING NORMAL, BENIGN CYST, CANCER, AND CALCIFICATION** * Image of a mammogram showing a normal mammogram, a benign cyst, a cancerous lesion, and a calcification.