Figure 1.

Cross-section of a bilayered duct. Secretory luminal cells (LEPs) are apically located to contractile myoepithelial cells (MEPs) and the basement membrane (BM). Milk proteins and cleaved Muc1 are secreted into the luminal space during lactation. Desmosomes containing desmoglein (Dsg)2 and desmocollin (Dsc)2 form between adjacent luminal cells and between adjacent LEPs and MEPs. Desmosomes between MEPs contain Dsg3 and Dsc3. MEPs as contractile cells contain smooth muscle actin and adhere to the BM via hemidesmosomes.