Before implantation, the blastocyst obtains its nutrition from the uterine endometrial secretions. How does the blastocyst obtain nutrition during the first week after implantation?

Correct Answer: D

Rationale: Step 1: The trophoblast cells of the blastocyst invade the endometrial lining during implantation. Step 2: The trophoblast cells secrete enzymes to digest the nutrient-rich endometrial cells. Step 3: The digested nutrients are absorbed by the trophoblast cells. Step 4: These nutrients are then utilized by the blastocyst for its growth and development. Step 5: This process ensures that the blastocyst receives the necessary nutrition for the first week after implantation. Summary: A: Incorrect. Endometrial secretions are no longer the source of nutrition after implantation. B: Incorrect. While the blastocyst may contain some stored nutrients, they are not sufficient for the first week post-implantation. C: Incorrect. The placenta is not fully functional until later in pregnancy, so it does not provide nutrition in the first week.

Correct Answer: C

Rationale: The correct answer is C: Head. The head of the sperm contains the nucleus, which houses the DNA. The nucleus carries the genetic information required for fertilization. The midpiece contains mitochondria for energy production, the flagellum provides motility, and the tail is a part of the flagellum. Therefore, the head is the only part of the sperm that houses the nucleus and DNA, making it the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Secondary oocyte. After meiosis I, the primary oocyte forms a secondary oocyte. The secondary oocyte is the cell that can be fertilized by a sperm to form a zygote. Polar bodies are products of oogenesis that do not participate in fertilization. Oogonium is a primordial germ cell in the ovary that undergoes mitosis to form primary oocytes. Therefore, the secondary oocyte is the only viable option for fertilization among the choices provided.

Correct Answer: C

Rationale: The correct answer is C: interstitial cell. Bladder infections are commonly referred to as cystitis, which is the inflammation of the bladder. Interstitial cells are found in the bladder wall and play a role in bladder function. Choice A, seminiferous tubule, is incorrect because it is a structure in the testes involved in sperm production. Choice B, nephritis, refers to inflammation of the kidneys, not the bladder. Choice D, diverticulitis, is inflammation of the diverticula in the colon, not related to bladder infections. Therefore, the most appropriate term for bladder infections is interstitial cell.

Correct Answer: B

Rationale: The correct answer is B: menarche. Menarche refers to the onset of a female's first menstrual period, not related to male reproductive anatomy. Choice A, labor a male's testis, involves the process of childbirth and is not related to male reproductive anatomy. Choice C, seminiferous tubule, is a part of the male reproductive system where sperm is produced. Choice D, menstruation, is the monthly shedding of the uterine lining in females, not related to male reproductive anatomy. Therefore, menarche is the only choice that does not pertain to male reproductive anatomy.