• The breast is a specialization of the integumentary system comprising skin, the mammary glands proper and abundant fat and connective tissue. Its principle function is milk production (lactation).



• The nipple contains smooth muscle fibers that increase its firmness and length to facilitate suckling.



• The nipple is surrounded by the pigmented areolar which contains the sebaceous areolar glands (of Montgomery). These glands secrete a protective lubricant for the nipple to minimize abrasion.



• The mammary glands proper are compound tubuloalveolar glands (modified sweat glands) which develop as invaginations of epidermal cells. The alveolar cells are compacted into 15-20 lobes each of which opens into a lactiferous duct. These ducts converge beneath the nipple where they widen into milk reservoirs (lactiferous sinuses) before narrowing again as several efferent ductules which open at the summit of the nipple.



• The lobes are embedded in fat and are compartmentalized by several broad fibrous suspensory bands (ligaments of Cooper) which connect the dermis with the loose connective tissue covering the deep pectoral fascia. This loose connective tissue permits the breast's mobility and is erroneously referred to as the retromammary space.



• As with other organs, the glandular tissue forms the parenchyma which is supported by the lipoareolar connective tissue stroma.

• The superolateral part of the subcutaneous breast tissue usually extends toward the axillary region as the axillary tail (of Spence). This should not be forgotten in self-examinations.



• The breast is supplied with cutaneous fibers from intercostal nerves 3-6. The autonomic components of these nerves supply the smooth muscles in the dermis, the nipple, the alveolar (acinar) clusters and in the walls of blood vessels. The parenchymal tissue is regulated by hormones.



• The breast receives its arterial blood supply from 3 primary sources:

A. Aorta - via intercostal arteries in intercostal spaces 3-5 (variable)

B. Subclavian artery - via the internal thoracic's perforating branches in intercostal spaces 3-5 (variable)

C. Axillary - via pectoral branches (from the thoracoacromial trunk) and the lateral thoracic

• The lymphatic drainage of the breast is very important due to metastatic carcinoma. From the perilobular plexus, lymph passes to the subareolar plexus and then via several trunks to the:

A. Axillary group of lymph nodes (75%)

B. Supraclavicular nodes

C. Infraclavicular nodes

D. Parasternal nodes and from these to the opposite side of the chest

* Frightening statistic: Carcinoma of the female breast is the most common form of cancer in the western civilized world, afflicting approximately 4% of all adult women, half of whom will die from it.