A man suffers from a disease that destroyed only the motor neurons of the spinal cord below the thoracic region. Which aspect of sexual function would not be possible?

Correct Answer: D

Rationale: The correct answer is D: Ejaculation. Motor neurons control muscle movements, including those involved in ejaculation. Since the motor neurons below the thoracic region are damaged, the man would not be able to ejaculate. Arousal (A), erection (B), and lubrication (C) are controlled by different mechanisms and do not solely rely on motor neurons in the spinal cord.

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.

Correct Answer: D

Rationale: The correct answer is D: spermiogenesis. Spermiogenesis is the process where spermatids mature into sperm cells in the testes. The gonads (testes in males) produce sex cells, but zygotes are formed through fertilization, not spermiogenesis. Mitosis is a type of cell division for growth and repair, not sperm production. Interstitial cells are found in the testes but are responsible for producing testosterone, not the maturation of spermatids into sperm cells. Therefore, option D is the correct choice as it specifically relates to the transformation of spermatids into sperm cells in the testes.