Which hormone plays a role in breast milk ejection (letdown) during lactation?

The reproductive system, also known as the genital system, is made up of anatomical organs and non-living substances that are responsible for sexual reproduction. The reproductive system has four functions: Produce egg and sperm cells: The primary reproductive organs, or gonads, are the ovaries and testes, which produce egg and sperm cells. Transport and sustain these cells: Secondary, or accessory, reproductive organs transport and sustain the gametes. Nurture the developing fetus: Accessory reproductive organs support the developing offspring. Produce hormones: Hormones regulate the... Show more

The reproductive system, also known as the genital system, is made up of anatomical organs and non-living substances that are responsible for sexual reproduction. The reproductive system has four functions:
Produce egg and sperm cells: The primary reproductive organs, or gonads, are the ovaries and testes, which produce egg and sperm cells.
Transport and sustain these cells: Secondary, or accessory, reproductive organs transport and sustain the gametes.
Nurture the developing fetus: Accessory reproductive organs support the developing offspring.
Produce hormones: Hormones regulate the normal physiology of the reproductive system and help develop sexual characteristics. 

A problem with the structure or function of either female or male reproductive system can cause infertility. 

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