Which of the following characterizes the secretory phase of a female's uterine (menstrual) cycle?

Correct Answer: C

Rationale: The secretory phase follows ovulation in the menstrual cycle. During this phase, the corpus luteum, formed from the ruptured follicle, secretes progesterone, maintaining the endometrium for potential implantation of a fertilized egg. Choice A is incorrect as ovulation occurs in the preceding phase (ovulatory phase). Choice B is incorrect as the functional layer of the endometrium thickens during the secretory phase to support a potential pregnancy. Choice D is incorrect as the functional layer of the endometrium is not shed during the secretory phase, but rather maintained for pregnancy support.

Correct Answer: A

Rationale: The correct answer is A: sperm. Sperm is not a component of semen; it is the male reproductive cell. Semen is composed of fluids from the epididymis, seminal glands, and prostate, which provide nourishment, protection, and transportation for sperm. The epididymis stores and matures sperm, seminal glands produce seminal fluid, and the prostate contributes prostatic fluid. Sperm is only a part of semen and not a component of it. Therefore, choice A is the correct answer.

Correct Answer: C

Rationale: The correct answer is C: blastocyst. At this stage of development, the embryo is a hollow ball of cells with an inner cell mass. This structure is called a blastocyst. A is incorrect because testosterone is a hormone, not a cell structure. B is incorrect as it does not describe the early stage of embryonic development. D is incorrect as luteinizing hormone is a hormone involved in the menstrual cycle, not embryonic development.

Correct Answer: D

Rationale: Step-by-step rationale: 1. Testosterone inhibits the release of luteinizing hormone (LH) through negative feedback. 2. LH is produced by the anterior pituitary. 3. Therefore, testosterone exerts negative feedback on the anterior pituitary to turn off LH secretion. 4. This maintains hormonal balance in the body. Summary of other choices: A. Incorrect because testosterone primarily affects LH secretion, not follicle stimulating hormone (FSH). B. Incorrect as it inaccurately suggests that testosterone turns off both LH and FSH secretion. C. Incorrect because Sertoli cells are involved in spermatogenesis, not LH regulation.

Correct Answer: C

Rationale: The correct answer is C: 400,000,000. During ejaculation, a healthy male typically releases around 200-500 million sperm cells. Choice A (4,000) and B (40,000) are too low compared to the average sperm count. Choice D (4,000,000) is also significantly lower than the typical sperm count, making it incorrect. Therefore, C is the correct answer as it aligns with the standard range of sperm count during ejaculation.