Lactiferous Duct - each lobe is drained by a single lactiferous duct that opens into the nipple. It is lined by a double layer of cuboidal or columnar cells surrounded by a sheath of connective tissue with myoid cells.
Lobules (#1 and #2) - enclosed by a thin layer of connective tissue.
Intralobular Ducts - lined by one or two layers of cuboidal cells surrounded by a thin layer of connective tissue.
Terminal Ductules (#1 and #2) - branches of intralobular ducts lined with cuboidal secretory cells.
During pregnancy, they differentiate into secretory alveoli that produce milk.
Alveoli (#1 and #2) - grow and expand during pregnancy and lactation.
Simple Epithelium - cuboidal or columnar secretory cells that synthesis and secrete milk.
Milk - the eosinophilic material within the alveolar lumen and ducts is proteins from secreted milk.