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 is the s...

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 groove 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 and nerves to pass to the arm 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 pulling very hard during a tug-of-war game)  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 pushing against resistance (e.g., pushing a car)  PECTORAL MUSCLES Muscle Proximal Attachment Distal Attachment Innervation Main Action Pectoralis Clavicular head: anterior surface Lateral lip of Lateral and medial Adducts and medially rotates major of medial head of clavicle intertubercular sulcus of pectoral nerves humerus; draws scapula Sternocostal head: anterior surface humerus anteriorly and inferiorly. of sternum, superior six costal Clavicular head flexes humerus cartilages, and aponeurosis of Sternocostal head extends it external oblique muscle from its flexed position Pectoralis 3rd to 5th ribs near their costal Medial border and Medial pectoral Stabilizes scapular by drawing minor cartilages superior surface of nerve it inferiorly and anteriorly coracoid process of against thoracic wall scapula Subclavius Junction of 1st rib and its costal Inferior surface of middle Nerve to Anchors and depresses clavicle cartilage third of clavicle subclavius Serratus External surfaces of lateral parts Anterior surface of Long thoracic Protracts scapula and holds it anterior of 1st-8th ribs medial border of scapula nerve against thoracic wall; rotates scapula 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, surrounded by a circular pigmented area of skin called the areola 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 determines the size of nonlactating breasts 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 pectoralis major towards the axillary fossa 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 space (bursa) 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 development The areolae and nipples also enlarge  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 – lactiferous sinus in which a small droplet of milk accumulates or remains in the nursing mother A --Duct. B --Lobule. C --Ampulla. D --Nipple. E --Fat. F --Pectoralis. G --Chest Wall. 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 Position varies especially in the multiparous woman  The mammary glands are modified sweat glands therefore they have no special capsule or sheath The rounded contour and most of the volume of the breasts are produced by subcutaneous fat, except during pregnancy when the mammary glands enlarge and new glandular tissue forms The milk secreting alveoli are are arranged in grape-like clusters In some women, the breasts may enlarge and become painful during the late luteal phase of the menstrual cycle These changes are most likely due to proliferation of the glandular tissues of the breast 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→ Axillary nodes through pectoral nodes Some drains directly to the deltopectoral/supraclavicular/interpectoral/inferior deep cervical nodes  LYMPHATIC DRAINAGE CONT’D Remaining lymph particularly from medial quadrants →parasternal nodes/opposite breast Lymph from lower quadrants → inferior phrenic (abdominal) nodes Lymph from skin of breast →axillary/inferior deep cervical/infraclavicular/parasternal nodes of both sides Lymph from axillary nodes→infraclavicular and supraclavicular→subclavian lymphatic trunk (drains lymph from upper limbs) Lymph from parasternal nodes→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 MAMMOGRAM SHOWING NORMAL, BENIGN CYST, CANCER, AND CALCIFICATION