Breasts are actually modified skin appendages that lie on the front surface of the chest wall. While it is present in both males and females, it is substantially larger in women and has specific functions that are otherwise inconsequential in men. The breast undergoes significant changes with puberty. This is driven entirely by the changes in hormones and is in preparation for nourishing offspring should pregnancy occur within the reproductive years. In order to understand the differences between the prepubertal and postpubertal breast, it important to have a knowledge about its structure.
The breast tissue is covered by the skin on the surface. Two prominent areas are the areola and nipple. The breast tissue under the skin can be divided into the functional tissue (intralobular stroma) and supportive tissue (interlobular stroma). The supportive tissue comprises fatty tissue and connective tissue. It provides strength and protection for the breast and the fat cells are rich store of energy for milk production. The functional tissue is made of secretory cells that are arranged into acini (alveoli). The cells empty its secretions into channels that run into ductules and then into terminal ducts. Groups of alveoli jointly make up lobules in the breast and these lobules are essentially teh functional components of the breast. Ductules eventually drain secretions into the lactiferous ducts which carry the milk to the nipple for expulsion into the exterior.
The Breast Before Puberty
The female breast has minimal fatty tissue prior to puberty and this accounts for its small size. The areola and nipple are also small in size. The channels in the breast end with the terminal ducts and lobular formation is at the minimum. The breast tissue cannot produce milk and is not at a point where it can even be prepared to do so within a short period of time. This is in conjunction with the reproductive system’s inability to release egg cells or sustain a fetus.
The Breast After Puberty
After puberty the fat accumulation in the breasts increases tremendously, largely driven by the effects of the hormones estrogen and progesterone. Lobules begin to form but are not fully active or structurally complete for breast milk production and secretion. A common misconception is that the postpubertal breast has the ability to produce milk prior to pregnancy. It is only once pregnancy occurs that the final structural changes are complete for milk production. Nevertheless, the postpubertal breast is structured such that these final changes can occur rapidly to make it fully functional. The size of the breasts, which are an aesthetic concern for many women, is determined both by hormonal and genetic factors. It does not represent a woman’s ability or inability to fall pregnant unless there is underlying pathology.
Female Breast in Pregnancy
Once pregnancy occurs, the lobules take on a more definitive shape. The breast size also increases substantially at this time due to fat accumulation. Both the areola and nipple enlarge. The duct system completes its development and these changes gradually progress throughout pregnancy. It is fueled by the elevated levels of estrogen and progesterone in pregnancy. However, the action of another hormone known as prolactin is important to fully activate the milk production feature of the female breast.
When the levels of estrogen and progresterone drop after childbirth, prolactin levels surge and the breast tissue starts producing milk. Suckling stimulates the breast and along with the constant drainage of milk, prolactin levels are maintained for milk production. The functional breast tissue remains active and the fat stores in the breast are maintained at a high level during this entire period. Discontinuing breastfeeding, will eventually ‘deactivate’ milk production and the quantity of fat tissue reduces slightly.