MCAT Question A Day - 7/9/14 - Answer!
Decreasing progesterone levels during the luteal phase of the menstrual cycle are associated with:
A. thickening of the endometrial lining in preparation for implantation of the zygote.
B. increased secretion of LH, leading to the luteal surge and ovulation.
C. degeneration of the corpus luteum in the ovary.
D. increased secretion of estrogen in the follicle, leading to the flow phase of the menstrual cycle.
C is correct. Decreased progesterone secretion results from the degeneration of the corpus luteum, which occurs because fertilization of the egg and implantation didn't happen. A is out because thickening of the endometrial lining occurs while estrogen and progesterone levels are high, not while progesterone secretion is decreasing. B is out because increased estrogen secretion causes the luteal surge, and because the luteal surge occurs earlier in the cycle. D is out because, while the flow phase does follow decreased progesterone secretion, it does not occur as a result of increased estrogen secretion.
C is correct. Decreased progesterone secretion results from the degeneration of the corpus luteum, which occurs because fertilization of the egg and implantation didn't happen. A is out because thickening of the endometrial lining occurs while estrogen and progesterone levels are high, not while progesterone secretion is decreasing. B is out because increased estrogen secretion causes the luteal surge, and because the luteal surge occurs earlier in the cycle. D is out because, while the flow phase does follow decreased progesterone secretion, it does not occur as a result of increased estrogen secretion.
Want more questions? - Click here to check out our MCAT Question A Day archive
