Following ejaculation, arterial blood flow into the corpora cavernosa decreases back to the normal resting level resulting in the flaccid state. What is the best explanation for this decrease in blood flow?

Correct Answer: C

Rationale: The correct answer is C because the resistance of the arterioles supplying the corpora cavernosa increases. This occurs due to the contraction of smooth muscle in the arterioles stimulated by sympathetic nervous system activity post-ejaculation. This constriction of arterioles reduces blood flow into the corpora cavernosa, leading to the flaccid state. Choice A is incorrect because systemic arterial pressure does not decrease significantly post-ejaculation. Choice B is incorrect as decreased sympathetic stimulation would actually lead to vasodilation, not vasoconstriction. Choice D is incorrect because the release of nitric oxide by the parasympathetic nervous system would lead to vasodilation, not vasoconstriction.

Correct Answer: C

Rationale: The correct answer is C: luteinizing hormone (LH). LH is released by the anterior pituitary gland to trigger ovulation in females. It causes the mature ovarian follicle to release an egg during the menstrual cycle. Antidiuretic hormone (A) is involved in regulating water balance, not ovulation. Thyroid-stimulating hormone (B) stimulates the thyroid gland, not the ovaries. Follicle-stimulating hormone (D) helps in the development of ovarian follicles, but it is not responsible for triggering ovulation. Therefore, C is the correct answer as it directly stimulates the release of the egg during ovulation.

Correct Answer: B

Rationale: The correct answer is B: oogenesis. Oogenesis is the process of creating female gametes (eggs) through meiosis in the ovaries. Spermatogenesis (A) is the process of creating male gametes (sperm). Spermiogenesis (C) is the final stage of spermatogenesis where spermatids mature into sperm. Cleavage (D) refers to the rapid cell divisions that occur after fertilization. Therefore, B is the correct answer as it specifically relates to the formation of female gametes.

Correct Answer: A

Rationale: The correct answer is A because follicle stimulating hormone (FSH) is not directly involved in the negative feedback loop for testosterone production. The negative feedback loop for testosterone involves the hypothalamus releasing GnRH, which stimulates the pituitary gland to release luteinizing hormone (LH), which then stimulates the Leydig cells in the testes to produce testosterone. Rising levels of testosterone inhibit the release of GnRH and LH through negative feedback to maintain hormonal balance. Choices B, C, and D are incorrect because they accurately describe components of the negative feedback loop for testosterone production.

Correct Answer: C

Rationale: The correct answer is C (28 days) because the typical ovarian and uterine (menstrual) cycles in a female are both around this duration. The menstrual cycle is typically 28 days, with ovulation occurring around day 14. This cycle is regulated by hormonal fluctuations and prepares the uterus for potential pregnancy. Choices A, B, and D are incorrect because a 7-day cycle is too short for a full menstrual cycle, a 14-day cycle is typically the duration of ovulation, and a 40-day cycle is longer than the average menstrual cycle length.