breakbone fever

breast The front of the chest or the mammary gland. The mammary gland is a milk-producing gland that is largely composed of fat. Within the mammary gland are sac-like structures called lobules, which produce the milk, as well as a complex network of branching ducts. These ducts exit from the lobules at the nipple. The lobules and ducts are supported in the breast by surrounding fatty tissue and ligaments. The breast contains blood vessels and lymphatics, but no muscles. The lymphatics are thin channels similar to blood vessels; they do not carry blood, but they collect and carry tissue fluid, which ultimately reenters the bloodstream. Breast tissue fluid drains through the lymphatics into the lymph nodes located in the armpit and behind the breastbone (sternum). The appearance of the normal female breast differs greatly among individuals and at different times during a woman’s life: before, during, and after adolescence; during pregnancy; during the menstrual cycle; and after menopause. The nipple of the breast becomes erect because of cold, breastfeeding, and sexual activity. The pigmented area around the nipple is called the areola. See also gland, mammary.