The external female reproductive organs include

Correct Answer: C

Rationale: The correct answer is C because the external female reproductive organs typically include the vaginal opening, the labia majora, and the clitoris. The vaginal opening is where sperm enters and a baby exits during childbirth. The labia majora are the outer folds of skin that protect the vaginal and urethral openings. The clitoris is a highly sensitive sexual organ that plays a key role in sexual pleasure. Option A is incorrect because it includes the mons pubis, which is not considered an external reproductive organ. Option B is incorrect because it includes the hymen, which is a thin membrane that may partially cover the vaginal opening but is not a consistent external organ. Option D is incorrect because it includes the ovaries, which are internal organs responsible for producing eggs, not external reproductive organs.

Correct Answer: A

Rationale: The correct answer is A: seminiferous tubules. Sperm production starts in the seminiferous tubules of the testes through a process called spermatogenesis, involving the division and maturation of germ cells. The other choices, B: epididymis, C: vas deferens, and D: ejaculatory duct, are incorrect as they are not sites of sperm production but rather play roles in sperm storage, transport, and ejaculation, respectively. The seminiferous tubules are specifically designed for sperm production, making them the correct choice in this context.

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.