Mechanism of Milk Production

Your breast is composed of 20 odd lobes, also called segments. Placed more or less at the periphery are the secreting alveoli, surrounded by the cells of my myoepithelium. The ducts from the alveoli converge to form a solitary duct of each segment, opening on the surface of the nipple. During pregnancy the breasts enlarge and the body prepares the ducts and alveoli for lactation. After delivery, a hormone, prolactin begins to act on the alveolar cells and induces milk production. Sucking the nipple by the infant cause withdrawal of the two hormones, estrogen and progesterone. Secretion of a higher amount of prolactin enhances production of fat, proteins and lactose by the glandular tissue. Thus the milk secretion is initiated by prolactin. Its maintenance is regulated by the growth hormone and thyroxine. The propulsion of milk into the ducts and then from the nipple into the baby’s mouth is again stimulated by sucking. Sucking is, thus, of vital importance for both the phases of lactation. If the breast is not fully emptied, increasing pressure in the ducts is likely to inhibit secretions. The higher the demand, the greater is the production and supply of milk. That is why some women keep secreting enough milk years after the birth of their last child.