The breasts are two prominences located on the upper ventral region of the torso among humans and other primates. Both sexes develop breasts from the same embryological tissues. The relative size and development of the breasts is a major secondary sex distinction between females and males. There is also considerable variation in size between individuals. Female humans are the only mammals which permanently develop breasts at puberty ; all other mammals develop their mammary tissue during the latter period of pregnancy; at puberty, estrogens , in conjunction with growth hormone , cause permanent breast growth.
In females, the breast serves as the mammary gland , which produces and secretes milk to feed infants. At the ends of the ducts are lobules , or clusters of alveoli , where milk is produced and stored in response to hormonal signals.
Along with their major function in providing nutrition for infants, several cultures ascribe social and sexual characteristics to female breasts, and may regard bare breasts in public as immodest or indecent. Breasts have been featured in ancient and modern sculpture, art, and photography. Breasts can represent fertility , femininity , or abundance. They can figure prominently in the perception of a woman's body and sexual attractiveness. Breasts, especially the nipples, can be an erogenous zone.
Breasts is often used to refer to female breasts in particular, though the stricter anatomical term refers to the same region on members of either sex. Male breasts are sometimes referred to in the singular to mean the collective upper chest area, [ a ] whereas female breasts are referred to in the plural unless speaking of a specific left or right breast.
A large number of colloquial terms for female breasts are used in English, ranging from fairly polite terms to vulgar or slang. Humans are the only mammals whose breasts become permanently enlarged after sexual maturity known in humans as puberty. The reason for this evolutionary change is unknown.
