Which of the following decreases the resistance in the arteries leading to the sinuses of the penis?

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: 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.

Correct Answer: D

Rationale: The correct answer is D: Development of breast tissue. This is not a secondary sex characteristic typical of males because breast development is a primary sex characteristic associated with females due to the presence of estrogen. In males, the secondary sex characteristics include deepening voice, increased growth of body hair, and enlargement of skeletal muscle mass due to the effects of testosterone. Breast tissue development in males, known as gynecomastia, is abnormal and can be caused by hormonal imbalances or certain medical conditions.