8.
The one follicle destined to ovulate each cycle is called the dominant follicle. It has relatively more FSH receptors and produces a larger concentration of estrogens than the follicles that will undergo atresia. It is able to continue to grow despite falling FSH levels.
9.
Sustained high estrogen levels cause a surge in pituitary LH secretion that triggers ovulation, progesterone production, and the shift to the secretory, or luteal, phase.
10.
Luteal function is dependent on the presence of LH. The corpus luteum secretes estrogen, progesterone, and inhibin-A, which serve to maintain gonadotropin suppression. Without continued LH secretion, the corpus luteum will regress after 12 to 16 days. The resulting loss of progesterone secretion results in menstruation.
11.
If pregnancy occurs, the embryo secretes hCG, which mimics the action of LH by sustaining the corpus luteum. The corpus luteum continues to secrete progesterone and supports the secretory endometrium, allowing the pregnancy to continue to develop.
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