Mammary Glands

Mammary Glands, source of milk for the young and a characteristic of all mammals. Although the mammary glands evolved recently in the development of vertebrates, their origin is uncertain. In monotremes (egg-laying mammals), they resemble sweat glands in structure, leading to speculation that mammary glands are sweat or sebaceous glands modified through evolution. In higher orders, the glands at maturity are developed in the female only; in monotremes they evolve equally in both sexes. The organ in human males occasionally develops functional ability, giving support to the belief that lactation occurred in both sexes in prehistoric mammals.

The development of mammary glands is regulated by hormones secreted by the anterior pituitary and the ovaries; lactation is under the control of the other pituitary hormones.

See also Breast.