During the week following ovulation, the endometrium increases in thickness to 5 to 6 millimeters. What stimulates this increase in thickness?

Correct Answer: C

Rationale: The correct answer is C: Progesterone from the corpus luteum. After ovulation, the corpus luteum forms from the ruptured follicle and secretes progesterone. Progesterone is responsible for preparing the endometrium for potential implantation of a fertilized egg by increasing its thickness. Luteinizing hormone (A) triggers ovulation but does not directly affect endometrial thickness. Estrogen from the corpus luteum (B) also plays a role in preparing the endometrium but does not specifically stimulate the increase in thickness. Follicle-stimulating hormone (D) primarily regulates the development of ovarian follicles and does not directly influence endometrial thickness.

Correct Answer: A

Rationale: The correct answer is A: spermatogonium. Spermatogonium is the primitive stem cell of spermatogenesis located at the periphery of seminiferous tubules. It undergoes mitosis to produce more spermatogonia or differentiate into primary spermatocytes. Spermatid and secondary spermatocyte are later stages in spermatogenesis, not the primitive stem cell. Primary spermatocyte is the immediate progeny of spermatogonium following differentiation.

Correct Answer: D

Rationale: The correct answer is D: LH triggers ovulation in a female. LH is a hormone released by the pituitary gland that stimulates the release of an egg from the ovary during the menstrual cycle. This process is known as ovulation. It is a crucial step in the reproductive cycle of females. A: LH does not promote the enlargement of female breasts. Breast growth is primarily regulated by estrogen and progesterone. B: LH does have a significant effect on females, particularly in the reproductive system. C: While LH does contribute to the development of secondary sex characteristics in females, its main role is in triggering ovulation.

Correct Answer: B

Rationale: The correct answer is B: oxytocin. Braxton Hicks contractions are irregular, painless contractions of the uterus that occur throughout pregnancy. Oxytocin is the hormone responsible for stimulating contractions during labor. Therefore, the presence of Braxton Hicks contractions indicates the preparation of the uterus for labor under the influence of oxytocin. Choices A, C, and D are incorrect as they do not directly relate to the physiological mechanism of Braxton Hicks contractions.

Correct Answer: D

Rationale: Step-by-step rationale for why the correct answer is D: 1. Testes are the male gonads responsible for producing sperm. 2. The testes function as the primary reproductive organ in males. 3. Sperm production occurs in the seminiferous tubules within the testes. 4. The testes also produce testosterone, the primary male sex hormone. Summary of why other choices are incorrect: A: Producing - While testes do produce sperm, this choice lacks specificity regarding the male gonads. B: Estrogen functions and are called ________ - Estrogen is a female sex hormone, not produced by male gonads. C: Progesterone - Progesterone is a female sex hormone produced mainly by the ovaries, not by male gonads.