Spermatogenesis is regulated by a negative feedback control system in which follicle-stimulating hormone (FSH) stimulates the steps in sperm cell formation. What is the negative feedback signal associated with sperm cell production that inhibits pituitary formation of FSH?

Correct Answer: B

Rationale: The correct answer is B: Inhibin. Inhibin is a hormone secreted by the testes in response to high levels of sperm production. Inhibin acts as a negative feedback signal to the pituitary gland, inhibiting the production of follicle-stimulating hormone (FSH). This helps to regulate spermatogenesis by preventing excessive FSH stimulation. A: Testosterone is not the negative feedback signal for inhibiting FSH production. While testosterone does play a role in regulating spermatogenesis, it does not directly inhibit pituitary FSH production. C: Estrogen is not involved in the negative feedback control system of spermatogenesis. Estrogen is more closely associated with the female reproductive system. D: Luteinizing hormone is not the negative feedback signal for inhibiting FSH production. LH is involved in the regulation of testosterone production, not FSH.

Correct Answer: B

Rationale: The correct answer is B: Rate of movement will decrease. Sperm cells require a slightly alkaline environment to maintain their motility. Lowering the pH to 4.5 will create an acidic environment, causing decreased sperm motility. Choice A is incorrect as lowering pH doesn't affect metabolic rate. Choice C is incorrect because prostaglandin E2 formation is not directly related to pH changes. Choice D is incorrect as oxygen consumption rate of sperm cells is not affected by vaginal pH.

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.