NCIt definition : The epithelium that lines the lactiferous ducts and the secretory alveoli. The mammary
epithelium in the lactiferous duct is a two layered epithelium. The basal cells are
cuboidal and the superficial cells are columnar. Branches of the lactiferous duct
are lined with a simple cuboidal epithelium. The secretory alveoli are lined by a
cuboidal or columnar epithelium. During the first half of pregnancy, the epithelium
undergoes considerable growth leading to the formation of new terminal branches of
ducts and of alveoli. The mammary glands continue to grow during the second half of
pregnancy due to increases in the height of epithelial cells and an expansion of the
lumen of the alveoli.;