Physiology of lactation – Anatomically, the breast is made up of glandular tissue, supporting tissue and fat. There are 20-25 alveoli in each breast, each lined by epithelial cells and surrounded by myoepithelial cells.
Milk is secreted in alveoli by epithelial cells and pushed forward by contraction of myoepithelial cells. Each alveoli drains its output via lactiferous tubules & ducts into — 10-15 lactiferous sinuses, which lie below the areola and open out onto the nipple. The size of the breast depends on the amount of fat and supporting tissue and does not reflect upon the milk-producing capacity.
Physiology of lactation depends on two interdependent processes in mother production of milk (Prolactin reflex), and secretion or ejection of milk (Oxytocin reflex), as well as actual sucking by the baby, dependent on neonatal reflexes.
A) Production of milk is a factor of Physiology of lactation (Prolactin reflex): When a baby sucks, afferent impulses from nipple stimulate prolactin secretion from anterior pituitary. Prolactin acts on the milk-producing alveolar epithelial cells to stimulate milk secretion. Thus, the prolactin reflex depends on how early, how often and how strongly the baby sucks.
Prolactin activity and milk production, which is another factor of Physiology of lactation, is facilitated by adequate emptying of breasts after each feed, early onset of lactation, frequent suckling, expression of breast milk, and night feeds.
Prolactin secretion is inhibited by pre-lacteal feeds, incorrect positioning and painful breast conditions physical or mental stress to mother.
B) Milk Ejection/Let down (Oxytoein reflex) is also a factor for Physiology of lactation and is also initiated during suckling when afferent impulses from nipple reach the posterior pituitary to stimulate oxytocin production. Oxytocin contracts the myo-epithelial cells surrounding the alveoli and lactiferous sinuses, to push the milk forward towards the nipple.
The squeezing sensation in the breast during Breast feeding is a sign of a good “let-down reflex”. Oxytocin secretion is affected by the physical and mental state of the mother.
In Physiology of lactation, Oxytocin activity and milk ejection is enhanced by Sight and sound of baby, pleasant thoughts of baby and maternal confidence in her ability to breastfeed.
Oxytocin secretion and milk ejection is reduced by — a) mother’s anxiety or low-confidence, b) mental stress or worry, and c) pain or discomfort during breast feeding.
C) Actual sucking by baby (Neonatal reflexes) is also a factor of Physiology of lactation: Three neonatal reflexes i.e. sucking, swallowing and rooting reflex participate in milk extraction during Breast feeding.
i) Rooting reflex helps the baby to latch onto the nipple. When the breast or nipple touches the baby’s chin, philtmm, upper lip or cheek, the baby opens his/her mouth to search for the nipple.
ii) Suckling reflex helps the baby to draw milk by converting the nipple and areola into a teat pressed between the lower jaw and hard palate. Wave-like movements of tongue facilitate sucking. For successful lactation, the baby should be well attached to the breast, with the nipple and most of the areola in his mouth.
iii) Swallowing reflex: In Physiology of lactation, After every 2-3 sucks, collected milk is swallowed by baby, followed by deep breath. Each suck-swallow-breathe cycle lasts for—i seconds.