Final answer:
Lactation is the process by which milk is synthesized and secreted from the mammary glands in response to an infant sucking at the nipple. It involves a neuroendocrine reflex triggered by sensory nerve fibers, resulting in milk secretion from lactocytes into the alveoli. The first few weeks of breastfeeding may involve leakage, soreness, and milk engorgement.
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 postpartum person, consuming the fat reserves stored during pregnancy.
When the infant suckles, sensory nerve fibers in the areola trigger a neuroendocrine reflex that results in milk secretion from lactocytes into the alveoli. The posterior pituitary releases oxytocin, which stimulates myoepithelial cells to squeeze milk from the alveoli so it can drain into the lactiferous ducts, collect in the lactiferous sinuses, and discharge through the nipple pores.
The first few weeks of breastfeeding may involve leakage, soreness, and periods of milk engorgement as the relationship between milk supply and infant demand becomes established.