Each spermatid and each ovum have ________. ________.

Correct Answer: D

Rationale: The correct answer is D: 23 chromosomes. Spermatids and ova are haploid cells formed through meiosis, containing only half the number of chromosomes (23) as a normal diploid cell. This is essential for maintaining the proper chromosome number when fertilization occurs. Glans penis and shaft of the penis (choices A and C) are structures related to the male reproductive system but are not present in spermatids or ova. Having 23 pairs of chromosomes (choice B) would result in a total of 46 chromosomes, which is incorrect for these gametes.

Correct Answer: D

Rationale: During the follicular phase, the correct answer is D because it is when the ovaries produce estrogen to stimulate the thickening of the uterine lining. This prepares the uterus for potential implantation of a fertilized egg. In contrast, choice A is incorrect because the corpus luteum is not formed until after ovulation. Choice B is incorrect as the corpus luteum forms after the egg is released. Choice C is incorrect because progesterone is mainly secreted during the luteal phase to maintain the uterine lining.

Correct Answer: D

Rationale: The correct answer is D because the first polar body is formed during the first meiotic division of the primary oocyte before birth. The primary oocyte undergoes meiosis I to form the secondary oocyte and the first polar body. This process occurs during fetal development, not after birth. Choice A is incorrect because the primary oocyte completes meiosis I to form the secondary oocyte and the first polar body before ovulation. Choice B is incorrect because the primary oocyte forms the first polar body before birth, not after birth. Choice C is incorrect because the first polar body is formed during meiosis I of the primary oocyte, not after fertilization.

Correct Answer: C

Rationale: The correct answer is C: Vulva. The vulva is the fleshy outer part of the female reproductive system that includes the labia majora, labia minora, clitoris, vaginal opening, and urethral opening. It is where the opening to the vagina is located. The uterus (A) is a hollow, muscular organ where the fetus develops during pregnancy. The ovary (B) is the female reproductive organ that produces eggs and hormones. Vaginitis (D) is inflammation or infection of the vagina, not the outer part of the reproductive system. Therefore, the correct answer is C as it accurately describes the external female genitalia where the vaginal opening is situated.

Correct Answer: B

Rationale: Step-by-step rationale: 1. FSH stimulates development of follicles in ovaries. 2. Follicle cells release estrogen. 3. Estrogen levels increase as follicles develop. 4. Estrogen plays key role in menstrual cycle regulation. Therefore, the correct answer is B (estrogen). Other choices are incorrect: A (hormones are broad, not specific), C (progesterone is released after ovulation), D (implantation occurs in the uterus, not ovaries).