To better understand galactorrhea, it helps to understand the anatomy of the breast.
Breasts are made of fat and milk glands. Small passageways, called ducts, deliver milk from the glands, to the nipple. Lymphatic tissue provides a passageway for cell waste to drain from the breast.
Examples of breast anatomy:
- Leung AK, Pacaud D. Diagnosis and management of galactorrhea. Am Fam Physician. 2004 Aug 1;70(3):543-50. 
- Verhelst J, Abs R. Hyperprolactinemia: pathophysiology and management. Treat Endocrinol. 2003;2(1):23-32.