Breasts are located on the anterior aspect of the chest and are composed of glandular tissue, adipose tissue, and ligamentous tissue. In women, breasts function to produce and secrete milk after childbirth, a process called lactation. The accessory reproductive glands, or mammary glands, are actually modified sweat glands responsible for lactation in women; they are present in men, but tend to be underdeveloped.

Supportive fibrous tissue, called Cooper's ligaments, is found throughout the breasts. These ligaments partially cover the lobes of glandular tissue, helping to bind the breasts together and give them shape. The nipples are externally located and serve as a passage for the milk to the environment. Each nipple is innervated by many nerves and contains smooth muscle. The nerves cause the nipples to be sensitive to external stimuli while the muscle fibers allow the nipples to become erect. A pigmented area called areola surrounds each...