Breasts are the tissue overlying the chest, or pectoral, muscles. They consist mostly of fatty and glandular tissues, but they also contain nerves, veins, and arteries. Ligaments and connective tissue support the breast and give it its shape. Dr. Malone, can you tell us more about the breast?
Sure, Dr. Patel. The tissue that makes up most of the breast is a complicated system of lobules and mammary ducts that look like bunches of grapes on their stems. Each breast contains 15 to 20 lobes in a circular pattern. The amount of fat covering the lobes determines the size of the breast. Each lobe is made up of lobules, and at the end of the lobules are tiny glands, or sacs, where milk is produced when a woman is breastfeeding. Up to one million lobules can be found in each breast. Muscle tissue around the lobules pushes the milk into the ducts.
The ducts carry the milk from the lobules to the nipple. There are usually 5 to 10 ductal systems in each breast, each with its own opening at the nipple. Small muscles in the nipple cause it to become erect in response to sexual stimulation or breastfeeding. The darker circle of skin around the nipple is called the areola, which contains glands that produce small amounts of fluid to lubricate the nipple when a woman is breastfeeding.
Hormones, including estrogen, progesterone, and prolactin, affect breast development and milk production. The levels of these hormones fluctuate according to a woman’s menstrual cycle. Pregnancy, menopause, and certain medications also affect these hormone levels.