A professional athlete in her mid-20s has not had a menstrual cycle for 5 years, although a bone density scan revealed normal skeletal mineralization. Which of the following facts elicited during the taking of her medical history may explain these observations?

Correct Answer: D

Rationale: The correct answer is D: Her plasma estrogen concentration is very low. The absence of menstrual cycles in a young athlete with normal bone density suggests hypothalamic dysfunction affecting the menstrual cycle. This can result from low estrogen levels, which are essential for the regulation of menstrual cycles. Low estrogen levels can be caused by intense physical activity, leading to suppression of the hypothalamic-pituitary-ovarian axis. Choice A is incorrect because a high-carbohydrate diet alone is unlikely to cause amenorrhea. Choice B is irrelevant to the absence of menstrual cycles and normal bone density in the athlete. Choice C, elevated blood pressure, is also unrelated to the situation described.

Correct Answer: D

Rationale: The correct answer is D: Ampulla of the fallopian tubes. Fertilization typically occurs in the ampulla of the fallopian tubes, where the sperm meets the egg. The ampulla is the widest part of the fallopian tube, providing the necessary space for fertilization to occur. Sperm must travel through the cervix and uterus to reach the fallopian tubes where fertilization takes place. The ovary is where the egg is released during ovulation but fertilization occurs in the fallopian tubes.

Correct Answer: D

Rationale: The correct answer is D because menopause occurs when the ovaries run out of follicles, which are needed for ovulation and hormone production. This leads to reduced estrogen levels and cessation of menstrual cycles. Choices A and B focus on hormone levels and follicle responsiveness, not the actual follicle count. Choice C is incorrect as progesterone is mainly produced by the corpus luteum after ovulation, not the primary cause of menopause.

Correct Answer: B

Rationale: The correct answer is B: vesicular (Graafian) follicle. A mature ovarian follicle ready for ovulation is called a vesicular follicle. It is the final stage before ovulation. A: primary oocyte is incorrect as it refers to an immature egg cell. C: ovum is incorrect as it refers to a mature egg cell after fertilization. D: corpus luteum is incorrect as it forms after ovulation and is responsible for producing progesterone, not the mature follicle.

Correct Answer: C

Rationale: The milky-colored fluid secreted from the prostate cleanses the urethra. This fluid helps neutralize the acidity of the urethra, providing a more suitable environment for sperm to survive. It does not enable sperm to swim or activate them, as these functions are performed by other components of semen. Additionally, it does not neutralize urine, as its primary function is to support sperm survival and motility.