Lactation describes the secretion of milk from the mammary glands, the process of providing that milk to the young, the period of time that a mother lactates to feed her young.
The process occurs in all female mammals, and in humans it is commonly referred to as breastfeeding or nursing. In most species milk comes out of the mother nipples, the platypus releases milk through ducts in its abdomen. In only one species of mammal, the Dayak fruit bat, is milk production a normal male function. In some other mammals, the male may produce milk as the result of a hormone imbalance. The phenomenon may also be observed in newborn infants as well for instance witch is milk.
Lactogenesis II, prolactin levels remain high, while the delivery of the placenta results in a sudden drop in progesterone, estrogen, and HPL levels. This abrupt withdrawal of progesterone in the presence of high prolactin levels stimulates the copious milk production of Lactogenesis II.
The breast is stimulated, prolactin levels in the blood rise, peak in about 45 minutes, and return to the pre breastfeeding state about three hours later. The release of prolactin triggers the cells in the alveoli to make milk.
Prolactin also transfers to the breast milk. Some research indicates that prolactin in milk is higher at times of higher milk production, and lower when breasts are fuller, and that the highest levels tend to occur between 2 a.m. and 6 a.m.
Other hormones notably insulin, thyroxine, cortisol are also involved, but their roles are not yet well understood. Biochemical markers indicate that Lactogenesis II begins about 30 40 hours after birth, mothers do not typically begin feeling increased breast fullness until 50–73 hours after birth.
Colostrum is the first milk a breastfed baby receives. It contains higher amounts of white blood cells and antibodies than mature milk, and is especially high in immunoglobulin A, which coats the lining of the baby immature intestines, and helps to prevent germs from invading the baby system. Secretory IgA also helps prevent food allergies. Over the first two weeks after the birth, colostrum production slowly gives way to mature breast milk.
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