Final answer:
The let-down reflex, triggered by oxytocin, is a neuroendocrine response necessary for the transfer of milk from the breast to the infant during lactation. Myoepithelial cells contract to move milk from alveoli to the nipple, facilitated by different stages of milk, including colostrum and mature milk.
Step-by-step explanation:
The process described is the let-down reflex, a biological response during lactation triggered by oxytocin release. This reflex is essential for breastfeeding as it allows milk to be expelled from the mammary glands and made accessible to the infant. When an infant suckles, sensory nerve fibers in the areola trigger a neuroendocrine response that results in the release of oxytocin from the posterior pituitary gland. Oxytocin then stimulates the contraction of myoepithelial cells that surround the alveoli, where milk is stored, leading to the milk being pushed through the lactiferous ducts and sinuses and eventually exiting through the nipple.
During different stages of lactation, different types of milk are produced. Colostrum, the initial milk, is rich in immunoglobulins, which help increase the newborn's immune defenses. As lactation continues, the milk changes from foremilk, which quenches the infant's thirst, to hindmilk, which is richer in fat and satisfies the infant's appetite.