Lactation in Human

The term lactation refers to the secretion and ejection of milk by the mammary glands.

Lactation is defined as the secretion and ejection of milk by the mammary glands of a female mammal, initiated after childbirth (parturition). The mammary glands undergo structural differentiation during pregnancy and start producing milk towards the end of pregnancy. This biological process enables the mother to nourish and immunologically protect the newborn.

The mammary gland is composed of 15–20 lobulated lobes, each containing clusters of secretory units called alveoli.

Two hormones govern lactation: Prolactin (milk production) and Oxytocin (milk ejection). They originate from different parts of the pituitary gland and act on different target cells.

1. Prolactin: "The Milk-Maker"

Source: Anterior pituitary gland
Role: Stimulates alveolar lactocytes to synthesise and produce milk (lactogenesis).

Prolactin Pathway:

Colostrum is the thick, yellowish, nutrient-rich fluid secreted by the mammary glands during the first 2–3 days after parturition. It differs substantially from mature breast milk in composition and serves a unique immunological role for the newborn.

Composition Highlights:

Special Constituents of Colostrum:

• Secretory IgA (sIgA): Coats the mucosal lining of the infant's GI and respiratory tracts, blocking pathogen attachment.
• Lactoferrin: Iron-binding protein with antimicrobial activity; inhibits bacterial and viral growth.
• Lysozyme: An enzyme that destroys bacterial cell walls.
• Leukocytes (immune cells): Provide direct cellular immunity to the newborn.
• Growth factors: Promote maturation of the infant's intestinal lining and immune system.

Type of Immunity Provided

• Breast milk provides all nutrients in suitable concentration and is completely digestible - unlike formula, which cannot replicate its biological complexity.
• It is a sufficient diet for infants for approximately 6 months of age.
• Provides both nutrition (proteins, fats, lactose, vitamins, minerals) and immunological protection(IgA, lactoferrin, leukocytes).
• Suckling stimulates oxytocin →uterine involution in the mother (uterus returns to pre-pregnancy size).
• No artificial feed can replace colostrum. WHO and all major health bodies recommend exclusive breastfeeding for the first 6 months.

• Lactation is the process by which mammary glands produce milk at the end of pregnancy, under the influence of the hormone Prolactin.
• The first milk secreted soon after childbirth is called Colostrum - it is sticky, yellowish and rich in proteins, lactose and antibodies (IgA); fat content is low.
• Antibodies (especially IgA) in colostrum provide passive immunity to the newborn when its own immune system is not yet fully developed.
• Lactation helps the mother in feeding and nourishing the newborn baby, providing all essential nutrients required in early life.