Lactation and Breast Feeding

Regulation of lactation - breast preparation • Pregnancy hormones trigger breast changes to prepare for feeding the new baby. • The amount of the hormone prolactin, essential to the initiation of lactation, increases steadily throughout pregnancy. • However, high levels of both estrogen and progesterone during pregnancy inhibit the action of prolactin on mammary tissue, so no milk production occurs. • After birth, levels of estrogen and progesterone drop and inhibition of prolactin action on the mammary glands ends. Milk formation (prolactin) • After parturition, the primary stimulus for prolactin production is the sucking action of the baby. • Stretch receptors in the breast send nerve impulses to the hypothalamus. • The impulses inhibit a prolactin-inhibiting hormone (PIH) and stimulate a prolactin- releasing hormone (PRH). • Increased PRH triggers the release of prolactin from the anterior pituitary. • Prolactin circulates to the alveoli of the mammary gland and promotes lactation. Relactation of lactation - milk ejection (oxytocin): • Once milk is formed it is ejected (let down) by the action of the hypothalamic hormone, oxytocin • The primary stimulus for oxytocin production is the sucking action of the baby. • Stretch receptors in the breast send nerve impulses to the hypothalamus. • The impulses stimulate the production of oxytocin. • Oxytocin circulates to the myoepithelial cells, surrounding the alveoli of the mammary gland, which contract and force the milk out of alveoli into the ducts where is can be suckled.

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