Lactation: Natural Processes, Physiological Responses and Role in Maternity

摘要

Lactation is of paramount importance to the survival, development, and growth of mammalian species. The mammary gland development starts during fetal life. The ductal development is particularly associated with puberty, and the alveolar development is associated with proliferative activity in the luteal phase of the reproductive cycle and in the early stages of pregnancy that leads to formation of the milk secreting unit. Parturition and lactation are two processes that are closely coordinated. Profound changes in several key hormones, such as progesterone, estrogen, prolactin, cortisol, placental lactogen, and insulin, occur early in pregnancy and parturition. These prepare and assure milk production by the mammary gland after delivery. For milk ejection, a neuro-hormonal reflex leading to the contraction of the myoepithelial cells surrounding the alveoli is stimulated by the action the oxytocin. After ceasing the stimulus for lactation, involution by apoptosis leads to regression of the mammary gland to the quiescent non-lactating state. Besides these physiological responses, the hormones can also influence cognitive functions and maternal behavior. Lactation is also important for establishing an affective linkage between mother and baby. This review will focus on natural processes of mammary gland development, on the hormonal control of lactation and on the role of breastfeeding in maternity.