Why is milk produced only after delivery, not before?
Correct Answer: B
Rationale: Correct Answer: B - High levels of progesterone and estrogen during pregnancy suppress milk production.
Rationale:
1. Progesterone and estrogen levels are high during pregnancy to maintain the uterine lining and support fetal development.
2. These hormones inhibit the action of prolactin, the hormone responsible for milk production.
3. As a result, the mammary glands are prevented from producing milk until after delivery when progesterone and estrogen levels drop.
4. Once these hormone levels decrease, prolactin can initiate milk production in response to the baby's demand for feeding.
Summary of other choices:
A: Levels of luteinizing hormone and follicle-stimulating hormone do not directly impact milk production during pregnancy.
C: Alveolar cells of the breast may have some developmental changes during pregnancy, but it is not the primary reason for milk production post-delivery.
D: Oxytocin is involved in milk ejection, not milk production, and its release is