Inside a woman's breast are 15 to 20 sections called lobes. Each lobe is made of many smaller sections called lobules. Lobules have groups of tiny glands that can make milk. After a baby is born, a woman's breast milk flows from the lobules through thin tubes called ducts to the nipple. Fat and fibrous tissue fill the spaces between the lobules and ducts.
The breasts also contain lymph vessels. These vessels are connected to small, round masses of tissue called lymph nodes. Groups of lymph nodes are near the breast in the underarm (axilla), above the collarbone, and in the chest behind the breastbone.
This picture shows the lobes and ducts inside the breast. It also shows the lymph nodes near the breast.