Which cells in the seminiferous tubules progress through the first meiotic division?

Correct Answer: D

Rationale: The correct answer is D: primary spermatocyte. Primary spermatocytes are the cells in the seminiferous tubules that progress through the first meiotic division. During this division, primary spermatocytes undergo DNA replication and then divide into two secondary spermatocytes. These secondary spermatocytes will then undergo the second meiotic division to produce haploid spermatids. Explanation for why other choices are incorrect: A: Sertoli cells are supporting cells in the seminiferous tubules but do not undergo meiotic divisions. B: Spermatogonia are the undifferentiated germ cells that give rise to primary spermatocytes but do not progress through meiotic divisions. C: Spermatids are the haploid cells produced after the two meiotic divisions, so they do not progress through the first meiotic division. In summary, primary spermatocytes are the cells that go through the first meiotic division in the seminiferous tubules

Correct Answer: C

Rationale: The correct answer is C because prostaglandin E2 plays a key role in initiating labor by promoting uterine contractions. Administering an antagonist of prostaglandin E2 effects would inhibit this process. Choice A is incorrect as progesterone levels decrease to trigger labor. Choice B is incorrect as luteinizing hormone does not directly influence labor initiation. Choice D is incorrect because mechanical dilation does not inhibit labor initiation but rather can facilitate it.

Correct Answer: B

Rationale: The correct answer is B: Nitric oxide. Nitric oxide is a potent vasodilator that relaxes smooth muscle in the arterial walls, leading to decreased resistance in the arteries. This results in increased blood flow to the sinuses of the penis, contributing to erectile function. A: Stimulation of the sympathetic nerves innervating the arteries would actually increase resistance by causing vasoconstriction. C: Inhibition of activity of the parasympathetic nerves leading to the arteries would also increase resistance as parasympathetic stimulation typically leads to vasodilation. Therefore, the correct answer is B as it directly causes vasodilation and decreases resistance in the arteries leading to the sinuses of the penis, which is essential for erectile function.

Correct Answer: C

Rationale: The correct answer is C: Estrogen. Before the preovulatory surge in luteinizing hormone, granulosa cells of the follicle primarily secrete estrogen. This hormone plays a crucial role in preparing the uterine lining for implantation and regulating the menstrual cycle. Estrogen also helps in the development of secondary sexual characteristics. Testosterone (Choice A) is mainly produced by the theca cells of the follicle. Progesterone (Choice B) is primarily secreted by the corpus luteum after ovulation. Inhibin (Choice D) is secreted by granulosa cells but primarily functions to inhibit follicle-stimulating hormone (FSH) secretion from the anterior pituitary gland.

Correct Answer: C

Rationale: The correct answer is C: Substance that blocks the actions of follicle-stimulating hormone. By blocking the actions of FSH, sperm production in the testes would be inhibited, leading to effective sterility. FSH plays a crucial role in stimulating sperm production, so blocking its actions would prevent the development of mature sperm. Explanation for why the other choices are incorrect: A: Substance that mimics the actions of luteinizing hormone - Mimicking LH would not necessarily lead to effective sterility in men. B: Substance that blocks the actions of inhibin - Inhibin regulates FSH secretion but blocking it would not directly lead to effective sterility. D: Substance that mimics the actions of gonadotropin-releasing hormone - Mimicking GnRH would not directly impact sperm production and sterility.