The hormone produced by the corpus

Correct Answer: A

Rationale: The correct answer is A. The hormone produced by the corpus luteum that helps maintain pregnancy is progesterone. After ovulation, the ruptured follicle forms the corpus luteum, which secretes progesterone to support the uterine lining for potential implantation. Choice B is incorrect as cleavage refers to early cell divisions in embryo development. Choice C is incorrect as fertilization is the fusion of sperm and egg. Choice D is incorrect as estrogen is primarily produced by the ovaries.

Correct Answer: D

Rationale: The correct answer is D: dilation stage. This is the stage of labor where the cervix dilates to allow for the passage of the baby through the birth canal. This stage is crucial for the progression of labor and eventual delivery of the infant. Option A, relaxin, is a hormone that helps soften the cervix and pelvic ligaments but is not directly related to the stage of labor mentioned. Option B, progesterone, is a hormone involved in maintaining pregnancy and preparing the uterus for implantation, not specifically related to the dilation stage. Option C, chorion, is a membrane surrounding the fetus and plays a role in nutrient exchange, not directly related to the dilation stage of labor.

Correct Answer: A

Rationale: After fertilization, the sperm and egg nuclei fuse to form a zygote. The egg completes its first meiotic division before fertilization, so A is incorrect. B is incorrect because the second polar body forms after fertilization. C is incorrect as the egg releases secretory vesicles to block polyspermy post-fertilization. D is incorrect as egg enzymes are activated post-fertilization to initiate embryogenesis. Thus, the answer is A, as the completion of the first meiotic division occurs before fertilization.

Correct Answer: A

Rationale: The correct answer is A because the corpus luteum does not contain the zona pellucida. The zona pellucida is a glycoprotein layer surrounding the oocyte, not the corpus luteum. The other choices are incorrect because B is true - the corpus luteum degrades if fertilization does not occur; C is true - corpus luteum derives from Latin for yellow body; and D is true - the corpus luteum develops from the remaining follicle after ovulation.

Correct Answer: C

Rationale: The correct answer is C: Menstruation. Menstruation is the process where the lining of the uterus sheds along with some blood once a month. This occurs in females who are not pregnant. Gestation (A) refers to the period of development of a baby in the womb. Conception (B) is the fertilization of an egg by sperm. Ovulation (D) is the release of an egg from the ovary. Menstruation best describes the shedding of the uterine lining and blood during a monthly period.