During the first few years after menopause, follicle-stimulating hormone (FSH) levels are normally extremely high. A 56-year-old woman completed menopause 3 years ago. However, she is found to have low levels of FSH in her blood. Which of the following is the best explanation for this finding?

Correct Answer: A

Rationale: The correct answer is A: She has been receiving hormone replacement therapy with estrogen and progesterone since she completed menopause. Hormone replacement therapy suppresses the release of FSH by providing exogenous hormones, thereby reducing the body's need to produce FSH. This explains the low levels of FSH in her blood despite being postmenopausal. Explanation for why the other choices are incorrect: B: Her adrenal glands continue to produce estrogen - Adrenal glands do produce small amounts of estrogen, but not in sufficient quantities to significantly impact FSH levels. C: Her ovaries continue to secrete estrogen - Ovaries cease estrogen production after menopause, so this would not explain the low FSH levels. D: She took birth control pills for 20 years before menopause - Birth control pills do not directly impact FSH levels in postmenopausal women.

Correct Answer: C

Rationale: The correct answer is C: The placenta secretes estrogen. The placenta is an endocrine organ that produces hormones, including estrogen, which plays a crucial role in maintaining pregnancy. Estrogen helps in regulating the menstrual cycle, promoting fetal growth, and preparing the body for childbirth. Choices A and B are incorrect because the placenta does not develop from granulosa cells and does not secrete luteinizing hormone. Choice D is incorrect because the placenta does not allow direct mixing of maternal and fetal blood; instead, it facilitates the exchange of nutrients and waste products between the mother and the fetus through a barrier called the placental barrier.

Correct Answer: C

Rationale: The correct answer is C because semen does not contain enzymes that enhance sperm motility. Sperm motility is primarily influenced by the structure and health of the sperm themselves. Semen aids in sperm transport, provides nutrients, buffers the acidic vaginal environment, and contains antibiotics. Enzymes in semen primarily help with liquefaction of semen after ejaculation, not sperm motility. Choices A, B, and D are incorrect because semen does dilute sperm, neutralizes the acidic vaginal environment, and contains antibiotic chemicals, respectively.

Correct Answer: B

Rationale: Certainly. The correct answer is B: Testosterone. Interstitial cells of the testis, also known as Leydig cells, synthesize and secrete testosterone. Testosterone is the primary male sex hormone responsible for the development of male reproductive tissues and characteristics. Estrogen (A) is primarily produced in the ovaries in females. Human chorionic gonadotropin (hCG) (C) is produced by the placenta during pregnancy. Luteinizing hormone (LH) (D) is secreted by the anterior pituitary gland and stimulates the interstitial cells to produce testosterone.

Correct Answer: B

Rationale: The correct answer is B: Day 14. Ovulation typically occurs around day 14 of a female's menstrual cycle. This is because ovulation is triggered by a surge in luteinizing hormone (LH) which usually happens midway through the cycle. Ovulation marks the release of an egg from the ovary, making conception possible. Days 7, 21, and 24 are not typically associated with ovulation as they are either too early or too late in the menstrual cycle for the surge in LH to occur. It is important to note that the timing of ovulation can vary among individuals and cycles, but day 14 is considered the average for a 28-day menstrual cycle.