QS Study


The process of formation and secretion of milk in the alveoli of breast and its expulsion from the mammary gland is called lactation. It is the secretion of milk by the mammary glands. The milk is produced by the mammary glands, which are contained within the breasts. It is a gland that secretes milk for suckling an infant or offspring.

Fig: the breast and its mammary gland

Phase: 4 phases

  1. Mammogenesis,
  2. Lactogenesis,
  3. Lactopoiesis,
  4. Ejection of milk.

Mammogenesis: It means the development of the breast. Female sex hormones act on stromal tissue, alveoli, and ducts of the breast at puberty.

  • Estrogen causes the development of stroma and duct,
  • Progesterone is responsible for the development of lobule and alveoli.

Lactogenesis: It means the synthesis of milk. It is initiated by the prolactin and is continued by the GH, thyroxin, and PTH. These three hormones form a modified solution of carbohydrate, protein, and fat.

Lactopoiesis: Continuation of lactogenesis by maintaining the secretion of lactotrophic hormones (LTH) is called lactopoiesis.

Ejection of milk: When a baby sucks the breast, stimulation from nipple passes to the hypothalamus which stimulates the posterior pituitary to secrete oxytocin which contracts myoepithelial cells of alveoli and initiates the ejection of milk.

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