310

breast can extend as far as the lateral margin of the pecto- ralis major muscle and into the axilla. In general, the breasts consist of secretory glands, superficial fascia and overlying skin, and subcuticular fat. Anatomically, in the pectoral region on each side of the anterior thoracic wall, the mammary glands are modified sweat glands in the superficial fascia anterior to the pecto- ral muscles and the anterior thoracic wall. 1 In each breast, the mammary glands and their associated duct systems are arranged in an array of lobules situated in a circumferential pattern around a central nipple, or papilla. In culmination, the ducts and the lobules converge to form approximately 20 lactiferous ducts that exit separate of one another onto the nipple. 1 Additionally, in relation to breast anatomy, the circular area of pigmented skin immediately surrounding the nipple is referred to as the areola. In each breast, a developed connective tissue stroma surrounds the individual ductal and lobule systems of the mammary glands. In certain regions, this connective tissue stroma condenses into ligaments. These are the suspensory ligaments of the breast, and are continuous with the dermal and epidermal tissue of the breast. In general, the suspenso- ry ligaments are responsible for supporting the independent structures of the breasts. 1 The lateral arterial blood supply to the breast provided by the vessels from the superior thoracic axillary artery, the thoracoacromial artery, the lateral thoracic artery and the subscapular arteries. 1 Additionally, the medial breast receives arterial blood flow through the branches from the internal thoracic artery, as well as through the second 3 Breast cancers account for about 30 percent of all cancer cases found inwomenand16percent of cancer deaths. The highest rates of breast cancer are in North America and Europe. through the fourth intercostal arteries via arterial branches that perforate the thoracic wall, and the overlying pectora- lis musculature. 1 Venous drainage from the breast occurs through veins that parallel the arteries and drain into the axillary, internal thoracic and intercostal veins. 1 The normal breast is innervated by a number of nervous branches. Innervation of the breast is via the anterior and later- j BREAST ANATOMY Breast profile: A. ducts, B. lobules, C. dialated section of duct to hold milk, D. nipple, E. fat, F. Pectorialus Ma or muscle, G. chest wall/rib cage. Enlargement: A. normal duct cells, B. basement membrane, C. lumen (center of duct). www. breastcancer.org al cutaneous branches of the second to sixth intercostal nerves. The nipple is innervated by the fourth intercostal nerve. 1 Nearly 75 percent of the lymphatic drainage of the breast drains laterally and superiorly to the axillary lymph nodes. The remaining lymphatic drainage occurs into the paraster- nal nodes, as well as through lymphatic vessels that follow the lateral branches of the posterior intercostal arteries. 1 The axillary lymph nodes, therefore, are the primary region to sample for cancer metastasis into the lymphatic system. In males, the breast anatomy differs greatly. The male breast is a rudimentary system composed of small ducts and strings of breast cells that do not typically extend beyond the areolar region of the male breast. B R E A S T P H Y S I O L O G Y The female breast is physiologically responsible for the pro- duction of milk for the purpose of nursing an infant. Specifi- cally, the mammary glands are responsible for the produc- tion of milk. These glands are present at birth in the female, 446 | The Surgical Technologist | OCTOBER 2009