Lactiferous Duct

Lactiferous Duct

Lactiferous ducts form a tree branched system connecting the lobules of the mammary gland to the tip of the nipple. They are also referred to as galactophores, galactophorous ducts, mammary ducts, mamillary ducts and milk ducts. 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. Within the areola, the lactiferous duct were thought to dilate to form the lactiferous sinus in which supposedly milk accumulates between breastfeeding sessions. However new research suggests that lactiferous sinus does not exist. 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.

The columnar epithelium plays a key role in balancing milk production, milk stasis and resorption. The cells of the columnar epithelium form tight junctions which are regulated by hormones and local factors like pressure and cassein content. Prolactin and/or placental lactogen are required for tight junction closure while progesterone is the main hormone preventing closure before birth.