Health Information

Development of mammary glands during pregnancy

During pregnancy, the mammary glands enlarge to a great extent and, there are marked changes in structure. During first half of pregnancy, the duct system develops further with appearance of many new alveoli. The gland secretes no milk now. During the second half, there is enormous growth of glandular tissues and the development is completed for the production of milk just before the end of gestation period.

Role of hormones in growth of mammary glands

Various hormones are involved in the development and growth of breast at different stages.

Estrogen

This cause growth and branching of duct system; so the normal development of duct system in breasts at puberty depends upon estrogen. Estrogen is also responsible for the accumulation of fat in breasts.

Progesterone

The development of stroma of the mammary glands depends upon progesterone activity. The development of glandular tissues also occurs by the activity of progesterone.

Prolactin

The activities of estrogen and progesterone prepare the mammary glands for milk secretion. But, these two hormones do not cause secretion of milk from the breast. Milk production from mammary glands depends upon Prolactin activity. Prolactin acts directly on the epithelial cells of mammary glands and cause localized alveolar hyperplasia, which is essential for milk production.

Other hormones

Growth hormone, thyroxine and cortisol enhance the overall growth and development of mammary glands in all stages.

Placental hormones

The estrogen and progesterone secreted from placenta are essential for further development of mammary glands during pregnancy. Both the hormones stimulate proliferation of ducts and glandular cells during pregnancy.