Lactation Physiology

Lactation is a complete process of milk synthesis and secretion including development of mammary gland (mammogenesis), initiation of milk synthesis and secretion (lactogenesis), maintenance of milk secretion (galactopoiesis), and restoration of virgin-like mammary gland (involution). Mammogenesis starts around 32 days of embryonic life but a series of structural and functional development, differentiation, and involution are noticed during different physiological state of animals. Lactogenesis is the biological process of onset of milk secretion which includes the enzymatic and cytological differentiation of mammary alveolar cells in early pregnancy to full lactation after parturition. The mammary gland utilized blood precursors to synthesize various milk components. Galactopoiesis is the maintenance of established lactation which follows a dynamic curve with a rapid accelerating phase, peak yield followed by a declining phage till the end of lactation. The suckling stimulus causes milk ejection from mammary gland by neuro-endocrine reflex. Mammary involution is a biological process to restore mammary gland into a virgin-like state through a series of tissue remodeling processes after the cessation of milk secretion. The interactions of different hormones and growth factors are essentially required in each stage of lactation process.