The ejaculatory duct is the union of the vas deferens and _____.

Correct Answer: A

Rationale: The correct answer is A: seminal vesicle. The ejaculatory duct is formed by the union of the vas deferens and the seminal vesicle. The seminal vesicle contributes seminal fluid that mixes with sperm from the vas deferens to form semen. The prostate gland surrounds the ejaculatory duct but does not directly join it. The ampulla is an enlarged portion of the vas deferens but does not directly connect to the ejaculatory duct. The urethra is the tube that carries urine and semen out of the body but is not part of the ejaculatory duct. Therefore, the correct answer is A because the seminal vesicle directly joins with the vas deferens to form the ejaculatory duct.

Correct Answer: B

Rationale: The correct answer is B: cervix. The cervix is the lower portion of the uterus that protrudes into the vaginal canal. It is located at the superior region of the vagina. The vaginal orifice (A) refers to the opening of the vagina, not the superior region. The hymen (C) is a thin membrane that partially covers the vaginal opening and is not related to the superior region. Vaginal rugae (D) are the ridges or folds in the vaginal wall that allow for expansion, which are not specific to the superior region.

Correct Answer: B

Rationale: The correct answer is B: estrogen. Estrogen is produced throughout the menstrual cycle by the ovaries. It plays a key role in regulating the menstrual cycle, promoting the growth of the uterine lining, and preparing the body for ovulation. FSH and LH are involved in stimulating the ovaries to produce estrogen and progesterone, respectively. Progesterone is mainly produced in the second half of the menstrual cycle, after ovulation, to support pregnancy. Therefore, estrogen is the hormone that is produced consistently throughout the menstrual cycle, making it the correct answer.

Correct Answer: D

Rationale: The correct answer is D: oxytocin. Oxytocin is the hormone responsible for initiating and sustaining labor contractions by stimulating the uterine muscles. It acts on the smooth muscle cells of the uterus to increase contractions. Estrogen (A) plays a role in preparing the uterus for labor but doesn't initiate contractions. HCG (B) is a hormone produced during pregnancy but is not directly involved in labor. Relaxin (C) helps relax the pelvic ligaments to facilitate childbirth, but it doesn't initiate contractions.

Correct Answer: A

Rationale: The correct answer is A: Placenta. The placenta is a temporary organ that connects a mammalian mother to its foetus by facilitating the exchange of nutrients, gases, and waste products between the mother and the developing baby. It also produces hormones necessary for pregnancy. Explanation of other choices: B: Chorion - The chorion is a membrane that surrounds the embryo and contributes to the formation of the placenta, but it is not the organ that directly connects the mother to the foetus. C: Endometrium - The endometrium is the inner lining of the uterus where implantation of the fertilized egg occurs, but it is not the organ that connects the mother to the foetus. D: None of the above - This choice is incorrect as the placenta is indeed the temporary organ that serves as the connection between the mother and the foetus in mammalian reproduction.