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.

Lactation is the process of producing and secreting milk from mammary glands, beginning towards the end of pregnancy. It is entirely driven by two key hormones

Hormonal Control

The Let-Down (Milk Ejection) Reflex:

1. Infant suckles at the nipple → sensory signals travel to the hypothalamus
2. The hypothalamus stimulates posterior pituitary to release oxytocin into the bloodstream
3. Oxytocin reaches the mammary glands and causes myoepithelial cells (surrounding alveoli) to contract
4. Contraction squeezes milk: alveoli → mammary tubules → mammary duct → ampulla → lactiferous duct → nipple

1. Colostrum: The First Milk

• Produced in the first 2–4 days after delivery
• Thick and yellowish in colour (due to carotenes and Vitamin A)
• Called "Liquid Gold" for its immune and nutritional properties

2. Mature Milk Composition

Mature breast milk contains the ideal balance of the following:

• Proteins (casein, whey) for growth
• Fats (fatty acids) for brain development
• Lactose (carbohydrate) for energy
• Vitamins and minerals for bone and immune development
• Enzymes and hormones for digestive maturation

• Breast milk provides all nutrients in suitable concentrations and is completely digestible – unlike formula, which cannot replicate its biological complexity.
• It is a sufficient diet for infants up to approximately 6 months of age.
• Provides both nutritional support (proteins, fats, lactose, vitamins, minerals) and immunological protection (IgA, lactoferrin, leukocytes).
• Suckling stimulates oxytocin → uterine involution in the mother (the 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 involves the mammary glands secreting and ejecting milk to nourish and protect the newborn, initiated after childbirth.
• Prolactin, released by the anterior pituitary, stimulates alveolar cells to produce milk, a process called lactogenesis.
• Oxytocin, from the posterior pituitary, triggers the let-down reflex by causing myoepithelial cells to contract and eject milk when the baby suckles.
• Colostrum, the initial yellowish milk produced for a few days post-birth, is low in fat but highly concentrated in proteins, lactose, and essential antibodies.
• The abundant IgA antibodies present in colostrum transfer crucial natural passive immunity to the infant, protecting them while their own immune system develops.