When lactogenesis occurs, under the influence of hormones, the milk is moved to the nipple by the action of smooth muscle contractions along the ductal system to the tip of the nipple.

[1][2] Lactiferous ducts are lined by a columnar epithelium supported by myoepithelial cells.

However past studies have shown that the lactiferous sinus does not exist.

The cells of the columnar epithelium form tight junctions which are regulated by hormones and local factors like pressure and casein content.

[4][5] The majority of breast diseases either originate from lactiferous ducts or are closely related.