Anatomy, Thorax, Breast

Excerpt

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 nipple is usually located just superior to the inframammary crease and is consistently found level along the midclavicular line and the fourth rib.

Glands

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.