Testosterone is secreted by

Correct Answer: A

Rationale: Testosterone is secreted by Leydig cells in the testes. Leydig cells are interstitial cells located between the seminiferous tubules. They are responsible for producing and secreting testosterone, which plays a crucial role in stimulating the development of male secondary sexual characteristics and maintaining male reproductive functions. Sertoli cells provide nourishment and support for developing sperm cells but do not secrete testosterone. Spermatocytes and early spermatids are involved in the process of spermatogenesis and do not secrete testosterone. Therefore, the correct answer is A because Leydig cells are specifically known for their role in testosterone production.

Correct Answer: B

Rationale: The correct answer is B: Stratum functionalis is shed during menstrual phase. The endometrium is composed of two layers - the stratum functionalis and the stratum basalis. The stratum functionalis is the layer that undergoes cyclic changes during the menstrual cycle, thickening and then shedding during menstruation. This process is essential for preparing the endometrium for potential implantation of a fertilized egg. Choice A is incorrect because the endometrium is actually lined by simple columnar epithelium with ciliated cells. Choice C is incorrect because the decidua is the name for the endometrium during pregnancy, but it is not specific to forming the decidua of the placenta. Choice D is incorrect because the arcuate artery is a branch of the uterine artery that runs along the myometrium, not penetrating the endometrium directly.

Correct Answer: A

Rationale: The correct answer is A: Cervical cancer. Cervical cancer can cause abnormal vaginal bleeding due to the presence of cancerous cells in the cervix. This can lead to spotting or bleeding between periods. Endometrial cancer (choice B) and endometrial carcinoma (choice D) specifically involve the endometrium, not the cervix. Leiomyoma (choice C) refers to uterine fibroids, which can cause heavy menstrual bleeding but are not typically associated with vaginal bleeding outside of menstruation. Therefore, the correct choice is A as it directly relates to per vaginal bleeding, while the other choices are not directly linked to this symptom.

Correct Answer: D

Rationale: The correct answer is D: in the fifth month of pregnancy. The testes begin to descend from the abdomen into the scrotum during the fifth month of pregnancy. This process is crucial for proper development and function of the testes. Descending at this stage allows for the testes to be positioned outside the body, which is essential for sperm production as it requires a slightly lower temperature than the internal body temperature. Summary: A: at birth - Incorrect, as the descent of the testes occurs during fetal development, not at birth. B: two months after birth - Incorrect, as the descent happens during pregnancy, not after birth. C: two months prior to birth - Incorrect, as the descent occurs during pregnancy, not prior to birth.

Correct Answer: B

Rationale: The correct answer is B: scrotum. The scrotum is a male-specific structure that houses the testes, which are responsible for producing sperm. In females, there is no homologous structure that serves the same function as the scrotum. The other choices (A: penis, C: prostate, D: bulbourethral glands) have homologous structures in females (clitoris, Skene's glands, and Bartholin's glands, respectively). This differentiation is based on the embryological development of male and female reproductive structures.