Breasts

From Encyclopedia of Sex and Sexuality

Women’s breasts contain mammary glands capable of secreting milk, marking humans as members of a mammalian species. This milk provides nourishment for the suckling infant from birth to weaning. Although they are not sex organs, breasts also have an unusual erotic significance in Western societies (see breasts as sex objects).

The breasts are two rounded organs. They consist largely of soft, fatty, and fibrous tissue on both sides of the female chest. Each breast contains fifteen or more groups of mammary glands, each with ducts that lead to the nipple at the tip of the breast. The nipples are cylindrical in shape and are usually flattened, but they easily become erect in response to the stimulation of touch or cold. The hormonal changes of pregnancy and childbirth usually cause enlargement of the breasts and nipples, as well as enlargement and darkening of the areolae, the circular areas immediately surrounding the nipples. When a woman delivers a baby, her body’s hormonal changes activate the mammary glands to begin the secretion of, first, colostrum, and then milk for nursing (see breast-feeding).

The development of the breasts begins as girls approach puberty, usually at nine to thirteen years of age, although it can begin earlier. Changes in the levels of sex hormones stimulate the growth of the fatty tissue of the breast, and the girl’s breast buds and nipples gradually become more prominent. There is a great variety in the size and shape of women’s breasts; popular stereotypes about “ideal” sizes and shapes have led many women to seek surgical changes in their appearance, usually to enlarge their breasts but in some cases to reduce their size. The size and appearance of the breasts does not seem to bear any relationship to a woman’s ability to nurse an infant.

The nipples are made up largely of smooth muscle fibers. They are sensitive because of their concentration of nerve endings. Breasts and nipples play an important role in the erotic play of some women; others report only mild erotic stimulation when partners caress and kiss them. Whatever is felt by a particular individual, erotic play with breasts and nipples is part of the usual sexual interaction in Western societies.