As a girl approaches adolescence, the first outward signs of breast development begin to appear. When the ovaries start to secrete estrogen, fat in the connective tissue begins to accumulate causing the breasts to enlarge. The duct system also begins to grow. Usually the onset of these breast changes is also accompanied by the appearance of pubic hair and hair under the arms.
Once ovulation and menstruation begin, the maturing of the breasts begins with the formation of secretory glands at the end of the milk ducts. The breasts and duct system continue to grow and mature, with the development of many glands and lobules. The rate at which breasts grow varies greatly and is different for each young woman.Female Breast Developmental Stages
Stage 1 (Preadolescent) only the tip of the nipple is raised
Stage 2 buds appear, breast and nipple raised, and the areola (dark area of skin that surrounds the nipple) enlarges
Stage 3 breasts are slightly larger with glandular breast tissue present
Stage 4 the areola and nipple become raised and form a second mound above the rest of the breast
Stage 5 mature adult breast; the breast becomes rounded and only the nipple is raised
