Definition of Breast

The mammary gland. Both men and women have breasts. Each person’s two breasts are close to but not exactly the same size and shape. Breasts vary widely in appearance among both men and women.

Breast Girl, Woman

At puberty the female sex hormones (primarily estrogens) in girls cause the glandular components of the breast to enlarge, establishing the potential to produce milk. The nipple also enlarges as does the glandular tissue surrounding it, the areola. Enlarged breasts are among the female secondary sexual characteristics.

Female breasts fill out with adipose (fatty) tissue and connective tissue in addition to its glandular structures, becoming rounded, and extend out from the chest. The male sex hormones (primarily testosterone) have the opposite effect in boys, causing the glandular components to all but disappear. In adulthood the male breasts remain relatively flat against the chest.

The glandular components of the adult female breast are the lactiferous glands, which can produce and secrete milk, and the lactiferous ducts, which store milk. Fatty tissue accumulates around these structures, called lobules. Supportive connective fibers called Cooper ligaments group the lobules into lobes. Each breast contains between 15 and 20 lobes.

Milk production, called lactation, occurs under the stimulation of prolactin, a hormone the pituitary gland begins to secrete after childbirth. Lactation may continue for as long as the woman continues breastfeeding. another hormone, oxytocin, stimulates the release of milk from the breast.

The breasts may become significantly larger (up to three times their prepregnancy size) while the woman is breastfeeding. When breastfeeding stops the lactiferous structures (glands and ducts) shrink and the breasts return to their normal size.

Sexual Stimulation

The breasts are also sources of sexual stimulation and arousal for women and for men, both by touch and visually. During sexual arousal and at orgasm the nipples become firm and erect. A woman’s breasts may become uncomfortably tender and sometimes swollen during the luteal phase of the menstrual cycle, in response to the elevation of estrogens in the blood circulation.

Menopause and Cancer

At menopause the glandular tissue in the breast shrinks and the breast structure becomes much less dense. At this time a woman’s risk for breast cancer increases significantly.

Current preventive health guidelines recommend routine mammogram (X-RAY of the breast) beginning at age 40 for most women, and beginning earlier and occurring more frequently in women who have high risk for developing breast cancer.

Health experts recommend that all women, beginning at the conclusion of puberty, perform monthly breast self-examination as a method of early detection for breast health concerns, including lumps that may be cancerous.

BREAST CANCERfibroadenoma

For further discussion of the breast within the context of the structures and functions of reproduction and sexuality, please see the overview section “The Reproductive System.”


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