Which hormonal mechanism is responsible for milk EJECTION during breastfeeding, as distinct from milk synthesis?

• A Prolactin release from the anterior pituitary in response to suckling
• B Progesterone withdrawal increasing alveolar permeability
• C Rising estrogen priming the ductal system
• D Oxytocin release from the posterior pituitary causing myoepithelial cell contraction ✓

Explanation

Suckling afferent impulses travel via the hypothalamus to trigger pulsatile posterior pituitary oxytocin release. Oxytocin contracts myoepithelial cells surrounding the alveoli, producing the let-down reflex. Prolactin, released from the anterior pituitary by the same suckling stimulus, drives milk protein and casein synthesis but does not eject stored milk. Estrogen and progesterone prime glandular development antenatally.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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