Lactation

LACTATION

• Process of milk secretion.

Preparations:

• Begins long before required.
• Breast development takes place at puberty.
• Further development occurs during pregnancy.

Phases of lactation:

• Divided into four phases
• Mammogenesis
• Lactogenesis
• Galactokinesis 
• Galactopoiesis.

1. Mammogenesis:

• Preparation of breasts.
• Involves both duct growth & lubulo-alveolar (lobule & secretory alveoli) growth.

Hormones involved:

• Estrogen – Proliferation & growth of mammary duct.
• Glucocorticoids – To mobilize amino acids.
• Growth hormone – To mobilize glucose.
• Insulin & Prolactin – To promote protein synthesis.
• Progesterone –  Development of lobuloalveolar system.

2. Lactogenesis:

• Synthesis & secretion of milk from breast alveoli.
• Hormone involved – Prolactin.

During pregnancy:

• No milk secretion despite higher prolactin level.
• Because estrogen & progesterone have direct inhibitory action on lactogenesis.

After parturition:

• Sharp fall in estrogen & progesterone levels.
• Inhibitory effect on lactogenesis removed & lactation occurs.

3. Galactokinesis/Milk ejection/Milk let-down:

• Hormone involved – Oxytocin
• Stimulates contraction of myoepithelial cells in mammary alveoli & lactiferous ducts.
• Released on nipple stimulation during sucking.

4. Galactopoiesis:

• Process of lactation maintenance.
• Hormone involved – Prolactin.