In mammals, a mammary duct is present in order to produce milk. The mammary duct is an organ, known as an exocrine gland. The mammary duct is an enlarged sweat gland. The mammary gland, or mammary duct, is composed of alveoli. Alveoli are a few millimeters in size and form cavities in the breast. These cavities fill with milk-creating cells called cuboidal cells. These cells are further surrounded by the myoepithelial cells. When the alveoli combine they care called lobules. In the anatomy of the nipple, the lactiferous duct drains from each of the lobules. The mammary gland is stimulated by oxytocin, which is released when an infant sucks on the breast. The milk that had been saved in the glands is now told to be released and secreted. In humans, the mammary glands are complex, composed of 10-20 simple mammary glands. It is possible to have more than two nipples, which is called polythelia, and more than two mammary glands, known as polymastia. The mammary duct will grow various times over the lifecycle of a human, including the embryonic stages and puberty stages.
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In Depth: Mammary duct