The shedding and bleeding of the decidua during menses is directly caused by low levels of _____.

Correct Answer: C

Rationale: The shedding and bleeding of the decidua during menses is directly caused by low levels of sex steroids. Sex steroids, specifically estrogen and progesterone, play a crucial role in maintaining the uterine lining. When levels of these hormones drop, it triggers the shedding of the decidua, leading to menstrual bleeding. FSH and LH are pituitary hormones that regulate the menstrual cycle but do not directly cause the shedding of the decidua. GnRH is a hypothalamic hormone that stimulates the release of FSH and LH.

Correct Answer: B

Rationale: LH (luteinizing hormone) stimulates Leydig cells to secrete testosterone by binding to its receptor on the Leydig cells, triggering the production and release of testosterone. GnRH (choice A) stimulates the release of LH, not testosterone directly. Inhibin (choice C) inhibits FSH secretion but does not directly stimulate testosterone production. DHT (choice D) is a metabolite of testosterone and does not stimulate Leydig cells to produce testosterone.

Correct Answer: B

Rationale: The correct answer is B: Testosterone. Testosterone promotes the final step of spermatogenesis, which is the maturation of spermatids into spermatozoa. Testosterone is essential for the development and maintenance of male reproductive tissues and secondary sexual characteristics. Choice A, Relaxin, is not involved in spermatogenesis. Choice C, Inhibin, regulates FSH secretion but does not directly promote the final step of spermatogenesis. Choice D, Estrogen, is a female sex hormone and not directly involved in spermatogenesis.

Correct Answer: C

Rationale: The correct answer is C: Oogonia. Oogonia are the cells that give rise to primary oocytes during fetal development. Oogonia undergo mitosis to produce primary oocytes, which then enter meiosis I to form secondary oocytes. Spermatogonia (A) are male germ cells that develop into sperm, not oocytes. Secondary oocytes (B) are formed from primary oocytes in the ovary after meiosis I completion. Granulosa cells (D) are somatic cells in the ovary that support oocyte development but do not give rise to oocytes themselves.

Correct Answer: C

Rationale: The correct answer is C: Mastopexy. This surgical procedure involves lifting and fixing a pendulous breast to the chest wall to achieve a more youthful and firmer appearance. It does not involve removal of breast tissue like in mastectomy (B) or creation of a new breast mound like in mastostomy (A). Mesopexy (D) is not a recognized surgical procedure for breast lifting.