Breast development is a vital part of reproduction in the female human. Unlike other mammals, however, human females develop full breasts long before they are needed to feed their children.
The development of the breast occurs at different stages throughout a woman’s life, first before birth, again at puberty and during the years of motherhood. Breasts also have changes during the menstrual cycle and when a woman reaches menopause.
The breasts begin to form during fetal development with a thickening in the area of the breast called the breast border or breast line. The moment a baby is born, the nipples and the beginnings of the milk duct system have been formed.
Breast changes continue to occur throughout life. The lobes, or small subdivisions of the breast tissue, develop first. The mammary glands then develop and consist of 15 to 24 lobes. The mammary glands are influenced by hormones that activate at puberty. Involution or retraction of the milk ducts is the final major change that occurs within the breast tissue. A gradual contraction of the mammary glands (involution) usually begins around the age of 35 years.
What changes occur in the breasts during puberty?
As a girl approaches adolescence, the first sign begins to appear out of the development of the breasts. When the ovaries begin to secrete estrogen, the fat in the connective tissue begins to accumulate and that causes the breasts to enlarge. The duct system also begins to grow. Generally, the onset of these breast changes is also accompanied by the appearance of pubic hair and hair in the armpits.
Once ovulation and menstruation begin, the maturation 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 speed at which the breasts grow varies enormously and is different for each young woman.
Stages of female breast development
Stage 1: (Preadolescence) only the tip of the nipple rises
Stage 2: Sprouts appear, breasts and nipples rise, and the areola (dark skin area surrounding the nipple) is enlarged
Step 3: Breasts are slightly larger with glandular tissue of the present breast
Step 4: The areola and nipple become protruding and a second mound forms on the rest of the breast
Step 5: Mature breasts of adult woman; The breasts become round and only the nipple rises
What cyclic changes happen to the breasts during the menstrual cycle?
Each month, women experience hormonal fluctuations that prepare the normal menstrual cycle. Estrogen, which is produced by the ovaries in the first half of the menstrual cycle, stimulates the growth of milk ducts in the breasts. The increasing level of estrogen leads to mid-cycle ovulation. Then the hormone progesterone takes control in the second half of the cycle, stimulating the formation of mammary glands. It is believed that these hormones are responsible for cyclical changes such as the inflammation, pain and sensitivity that many women experience in their breasts just before menstruation.
During menstruation, many women also experience changes in breast texture. Breasts are particularly bumpy. These are the glands in the breasts that are enlarging to prepare for a possible pregnancy. If the pregnancy does not occur, the breasts return to their normal size. Once menstruation begins, the cycle begins again.
What happens to the breasts during pregnancy and breastfeeding?
Many health care providers believe that breasts are not fully mature until a woman has given birth and produced milk. Breast changes are one of the earliest signs of pregnancy. It is a result of the hormone progesterone. In addition, areolas (the dark areas of skin surrounding the nipples of the breasts) begin to swell, followed by rapid swelling of the breasts themselves. Most pregnant women experience sensitivity underneath and to the sides of the breasts, and tingling or pain of the nipples due to the growth of the milk duct system and the formation of many more lobes.
In the fifth or sixth month of pregnancy, the breasts are fully capable of producing milk. As in puberty, estrogen controls the growth of ducts, and progesterone controls the growth of glandular outbreaks. Many other hormones, such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, oxytocin, and human placental lactogen (HPL), also play vital roles in milk production.
Other physical changes occur, such as the prominence of blood vessels in the breasts and the enlargement and darkening of the areola. All of these changes occur in preparation for breastfeeding the baby after birth.
What happens to the breasts at menopause?
When a woman reaches about 50 years of age, menopause begins or is in progress. At this time, the levels of estrogen and progesterone begin to fluctuate. Estrogen levels fall sharply. This leads to many of the symptoms commonly associated with menopause. With this reduction in estrogen stimulation of all body tissues, including breast tissue, there is a reduction in the glandular tissue of the breasts. Without estrogen, the connective tissue of the breasts becomes dehydrated and becomes inelastic. The breast tissue, which was prepared to produce milk, shrinks and loses shape. This leads to the “fall” of the breasts often associated with women of this age.
Women who are taking hormones may experience some of the premenstrual symptoms of breasts they had when they were still menstruating, which may include tenderness and swelling. However, if there were sagging breasts before menopause, this is not reversed with hormone therapy.