Cell types and morphogenesis in the mammary gland.

Abstract
Cell types present in the mammary gland and their evolution were studied by labeling female rats with radioactive thymidine at various phases of the estrous cycle. Apparently the stem cells for mammary development are present in the terminal end buds and they generate a lineage for luminal cells and possibly a distinct one for myoepithelial cells. Growth and differentiation are controlled by both hormones and local factors.