Which of the following could inhibit the initiating labor?

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: 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.

Correct Answer: C

Rationale: The correct answer is C: Seminal vesicles. Seminal vesicles produce a thick, yellowish secretion that provides nutrients and activates sperm. This secretion, along with sperm from the testes, forms semen. Bulbourethral glands produce a clear, viscous fluid that lubricates the urethra during sexual arousal (not yellowish). The prostate gland secretes a milky fluid that neutralizes acidic vaginal secretions. The ejaculatory duct is a passageway for semen to travel from the vas deferens to the urethra and does not produce any secretions. Therefore, the seminal vesicles are the correct answer as they specifically produce the described yellowish secretion that nourishes and activates sperm.

Correct Answer: C

Rationale: The correct answer is C: Progesterone. The corpus luteum produces progesterone, which is essential for maintaining the uterine lining and supporting early pregnancy. Progesterone helps prevent contractions of the uterus and supports the development of the placenta. Estrogen (A) is important for the initial thickening of the uterine lining but does not play a direct role in maintaining pregnancy. Testosterone (B) is not involved in pregnancy maintenance. Relaxin (D) helps relax the uterine muscles but is not primarily responsible for maintaining pregnancy.