Lactiferous ducts

Lactiferous ducts form a branched system connecting the lobules of the mammary glands to the tip of the nipple. They are the structures which carry milk toward the nipple in a lactating female.

Lactiferous ducts are lined by a columnar epithelium supported by myoepithelial cells. When a woman is not lactating, the lactiferous duct is frequently blocked by a keratin plug. This plug prevents bacteria from entering the duct in non-lactating women.

Most breast cancers arise from the ductal epithelium. The high susceptibility to benign and malignant diseases is in part a consequence of the cycling hormonal growth stimulation resulting in a high cell turnover and accumulation of defects.