The mammary glands are located on either side of the adult female chest, which with fatty tissue and the nipple make up the breast. Mammary glands are exocrine glands which release secretions through ducts. Circulating hormones including estrogen and growth hormone affect the development of ducts within the glands during various stages including puberty and pregnancy.
Cyclical changes in hormones can result in changes within the mammary glands including swelling, pain, and tenderness during menstruation. During pregnancy and lactation, oxytocin and prolactin influence developments within the mammary glands that allow for breastmilk to be secreted through the nipple via a system of ducts.