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How does oxytocin cause milk ejection during breast-feeding?
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Endocrine system
The glands of the human endocrine system.
During breast-feeding, oxytocin facilitates milk ejection through a process known as the milk-ejection reflex or "the draught." The mechanism functions as follows:
- Stimulation: When an infant begins to suckle, the physical stimulus on the nipples transmits nerve impulses to the hypothalamus in the brain.12
- Release: In response to these impulses, the pituitary gland releases stored oxytocin into the bloodstream.132
- Contraction: Oxytocin travels to the mammary glands, where it binds to specific receptors on myoepithelial cells (specialized smooth muscle cells) surrounding the alveoli and small ducts.132
- Ejection: The binding of oxytocin causes these muscle cells to contract, which squeezes the alveoli and forces milk into the ducts, making it available for the infant to extract.132
This process typically begins within seconds of the start of suckling. Because the reflex is sensitive to the nervous system, it can also be triggered by conditioned cues, such as the sound of a baby crying, or inhibited by stress, fear, or embarrassment.31