A breastfeeding mother notices milk dripping from the opposite nipple when her infant suckles on one breast. Which hormone and target cell mediate this milk ejection?

• A Prolactin acting on alveolar epithelial cells
• B Oxytocin acting on alveolar epithelial cells
• C Oxytocin acting on myoepithelial cells surrounding alveoli ✓
• D Prolactin acting on myoepithelial cells surrounding ducts

Explanation

Suckling stimulates a neuroendocrine reflex causing pulsatile oxytocin release from the posterior pituitary. Oxytocin contracts the myoepithelial cells that surround the alveoli, expelling stored milk into the ducts, which explains the let-down in the opposite breast. Prolactin is responsible for milk synthesis by alveolar epithelium, not for ejection, so pairing prolactin with myoepithelial cells is doubly wrong.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.