Development Of The Mammary Gland

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Introduction 1. Normal mammary gland 1.1 normal mammary gland anatomies The normal breast sits on the chest muscle, consisting mainly of adipose tissue, also known as mammary fat pad. The mature mammary gland is composed of 15-20 lobes, which are each composed of smaller structure called lobules. Tiny Lactiferous ducts connect lobules to each other. (Fig. 1b) (Schneider and Bocker). A typical structure of duct is composed of a hollow lumen, enclosed by a layer of epithelial luminal cells that produce milk (Fig 1c). Outside of epithelial luminal cells is a layer of myoepithelial cell and basement membrane (Visvader). Maintain the correct morphology of duct requires extracellular matrix which together with fibroblasts, endothelial cells, macrophages, and adipocytes, constitute mammary stroma. Fat fills the spaces between the lobules and ducts. 1.2 Mammary gland development Development of the mammary gland starts during embryogenesis but takes several years to complete; indeed, they are still primitive structures that are not yet connected to the nipple, therefore are not functional at birth (Anderson and Clarke). Until puberty, breasts grow extremely slow in size. However, at puberty, they undergo their first spurt of allometric growth and formation of the milk-producing lobules. The lobules extend into the mammary fat pad, and glands become more complex. During each menstrual cycle, ovarian hormones induce mammary development and new budding of structures up until the age of
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