Final answer:
Lactation is the process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast. Breast milk provides ideal nutrition and passive immunity for the infant, while the composition of breast milk changes during the first days of lactation and in the course of a single feeding.
Step-by-step explanation:
Lactation is the process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to an infant sucking at the nipple. Breast milk provides ideal nutrition and passive immunity for the infant, encourages mild uterine contractions to return the uterus to its pre-pregnancy size (i.e., involution), and induces a substantial metabolic increase in the mother, consuming the fat reserves stored during pregnancy. The composition of breast milk changes during the first days of lactation as the early milk, called foremilk, is watery, translucent, and rich in lactose and protein, while hindmilk, delivered toward the end of a feeding, is opaque, creamy, and rich in fat.