Health Information

Lactation refers to synthesis, secretion and ejection of milk. It consists of two processes milk secretion and milk ejection.

Milk secretion

Synthesis of milk by alveolar epithelium and its passage through the duct system is called milk secretion. This process has two phases initiation of milk secretion or lactogenesis and maintenance of milk secretion or galactopoiesis.

Initiation of milk secretion or lactogenesis

Although small amount of milk secretion occurs at later months of pregnancy, a free flow of milk occurs only after the delivery of the child. The milk is secreted initially before parturition is called colostrums. This contains almost all the components of milk except fat.

Role of hormones in lactogenesis

During pregnancy particularly in later months, more quantity of Prolactin is secreted. But the activity of this hormone is suppressed by estrogen and progesterone secreted by placenta. Because of this lactation is prevented during pregnancy. Immediately after the delivery of the baby and expulsion of placenta, there is sudden loss of estrogen and progesterone. Now, the Prolactin is free to exert its action on breast and to promote lactogenesis.

Maintenance of milk secretion or galactopoiesis

Prolactin is important for initiation of milk secretion rather than maintenance of milk secretion. Galactopoiesis depends upon other hormonal factors like growth hormone, thyroxine and cortisol, which are essential for continuous supply of glucose, amino acids, fatty acids, calcium and other substances, which are essential for the production of milk.

Role of hypothalamus in galactopoiesis

The galactopoiesis occurs up to 7 to 9 months after delivery of child. The impulses from touch receptors around the nipple stimulate hypothalamus. This in turn causes secretion of Prolactin from anterior pituitary. Prolactin acts on glandular tissues and maintains the functional activity of breast for subsequent nursing.

Milk ejection

The discharge of milk from mammary gland depends upon contractile mechanism in breast, which expels milk from alveoli into the ducts. Milk ejection is a reflex phenomenon it is also called milk reflex or milk let down reflex. It is a neuroendocrine reflex.