Structure & Function
Breast Cancer

The main parts of the female breast are lobules (milk producing glands), ducts (milk passages that connect the lobules and the nipple), and stroma (fatty tissue and ligaments surrounding the ducts and lobules, blood vessels, and lymphatic vessels).

Adult women have 15 to 20 lobes in each breast. Each lobe has 20 to 40 lobules. Small ducts are attached to the lobules. These ducts join together like branches of grape stems into increasingly larger ducts. There are about ten duct systems in each breast, each with its own opening at the nipple.

Muscle tissue in the nipples allows them to become erect in response to stimulation or breastfeeding. Muscle tissue around the lobules helps squeeze milk into the ducts. Glands on the areola (the shaded circle of skin around the nipple) secrete small amounts of fluid to lubricate the nipple when breastfeeding.