The anatomy of the breast must be well understood to understand the disorders that affect this organ and develop a plan for breast surgery. When examined, some degree of asymmetry is noted in most breasts. Other deformities include kyphosis, scoliosis, or some type of pectus deformity.
The majority of the breast consists of glandular (milk-producing) and fatty tissues. However, the ratio of the glandular to fatty tissue varies among individuals. The breast is heavily influenced by the sex hormone estrogen. As menopause approaches, the levels of estrogen declines which also decreases the glandular tissues.
The pectoralis major muscle forms the base of the breast, which extends from the second to sixth rib early in life but may extend to below the sixth rib as the breast matures and sags. The breast is anchored to the pectoralis major fascia by the Cooper ligaments. However, these ligaments are flexible and allow for movements in the breast. In most women, the Cooper ligaments become stretched with time and age, eventually resulting in a ptotic breast. Because of gravity, the lower pole of the breast is fuller than the upper pole. At the lateral edges of the breast, the tail of Spence extends in the axilla.
The underlying breast is made of glandular (milk-producing) and fatty tissue. The ratio of fat versus glandular varies depending on age, post-menopausal, post-partum, or pregnancy status. At the onset of menopause, a decline in the levels of estrogen results in a decrease in glandular tissue and an increase in fatty tissue.
The nipple plays an important role in breastfeeding. The minimal nipple length required for successful breastfeeding is about seven millimeters. However, the nipple shows great variation in topography; it can be flat, short, and even inverted, which can hamper breastfeeding in some women.
Breast development or mastogenesis starts around the sixth week of gestation. The milk line, which is a distinct linear elevation, appears around the seventh week. At the end of the eighth week, the rudimentary breast forms from the thickened white line and will eventually become the mature breast. Throughout embryogenesis, there is a proliferation of basal cells. At about 30 weeks of gestation, occlusion of the papillary bag results in the formation of the nipple areolar complex. The final nipple will appear at about 38 to 40 weeks.
The breast skin receives its blood supply from the subdermal plexus; these tiny blood vessels, in turn, communicate with deep underlying arterioles which supply the breast parenchyma. Blood is supplied to the breast from the following vessels:
Overall, at least 60% of the blood supply is from the superomedial perforators which come off the internal mammary artery.
The breast also has profuse venous drainage divided into the superficial and deep veins. The superficial veins are found along the anterior surface of the fascia; these veins follow the areola path under the nipple areolar complex, often referred to as the venous plexus of Haller. Deep inside the breast are many large veins which drain into the chest wall veins.
The breast also has extensive lymphatic drainage that runs both superficially and deep within the breast. The superficial lymphatics are the areolar and subareolar plexus. The latter also receives lymphatics from glandular tissues. The superficial lymphatics continue posteriorly and medially and eventually reach the axillary lymph nodes.
Sensory innervation to the breast is derived from branches of the intercostal nerves T3-T5. Other nerves that supply sensory innervation include the lower cervical plexus. Sensation to the nipple is derived from the lateral cutaneous branch of T4.
On the lateral and medial wall of the chest, the base of the breast sits over the serratus anterior and external oblique muscles.
Several anomalies of the nipple have been recognized, including the following:
In women with breast cancer, several types of surgical procedures are done including a lumpectomy and modified mastectomy. Unlike in the past, total or radical mastectomy is done less frequently. Several studies have shown that skin-sparing or modified radical mastectomies are effective in the treatment of breast cancer. However, there is a small risk of breast cancer recurrence.
The breast is susceptible to many benign and malignant disorders, including the following:
The leading cause of death in women is breast cancer. In addition, breast cancer is one of the most common malignancies of women worldwide. Many risk factors for breast cancer have been identified, but it is important to ensure that women over the age of 45 have regular mammograms, eat a healthy diet, exercise, and refrain from smoking.
Male breasts develop from the same embryological cells as females. However, males have a lower production of estrogens and a higher production of androgens. In some men, the breasts may grow quite large as a consequence of an imbalance between estrogens and testosterone. About two-thirds of boys will have some type of temporary gynecomastia which resolves within 24 months. Sometimes gynecomastia can be caused by medications like digoxin and spironolactone.
Cosmetic surgery is often performed to augment or reduce the size of the breasts. In other cases, plastic surgery is done to reconstruct a deformed breast, especially in women who undergo surgery for breast cancer. Both breast lifts and breast augmentation are strictly cosmetic procedures, whereas a breast reduction in women is often done for medical reasons (back or neck pain). Sometimes, breast reconstruction is done for asymmetrical breasts.
Breast augmentation, when done properly, does not interfere with a woman's ability to breastfeed. However, breast reduction surgery is known to damage the nerves in the nipple areolar complex and lead to a decreased sensation. In addition, many women who have had breast reduction surgery may not be able to breastfeed because the glandular tissues have been removed. Finally, it is important to know that breast implants can interfere with mammography.
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