Female BreastDevelopment

Breast development is a vital part of reproduction in the human female. Unlike other mammals, however, human females develop full breasts long before they are needed to nurse their offspring.

Breast development occurs in distinct stages throughout a woman's life, first before birth, again at puberty, and during the childbearing years. Changes also occur to the breasts during the menstrual cycle and when a woman reaches menopause. Breasts begin to form during fetal development with a thickening in the chest area called the mammary ridge or milk line. By the time a female infant is born, nipples and the beginnings of the milk-duct system have formed. Breast changes continue to occur over the lifespan, with lobes, or small subdivisions of breast tissue, developing first. Mammary glands develop next and consist of 15 to 24 lobes. Mammary glands are influenced by hormones activated in puberty. Involution or shrinkage of the milk ducts is the final major change that occurs within the breast tissue. A gradual shrinking of the mammary glands (involution) typically begins around the age of 35.