Question

select the correct answer.
what hormonal change occurs after fertilization that causes the endometrial lining to remain intact so that the fertilized egg can successfully implant in it?
a. the pituitary gland secretes oxytocin and maintains the endometrial lining.
b. the pituitary gland secretes follicle stimulating hormone, which acts on the follicles and stimulates them to produce progesterone.
c. the hypothalamus secretes gonadotropin releasing hormone, which maintains the endometrial lining.
d. the membrane surrounding the embryo secretes human chorionic gonadotropin, which prevents the corpus luteum from disintegrating.
e. the developing embryo prevents the production of progesterone after the breakdown of the corpus luteum to maintain the endometrial lining.

Explanation:

• Option A: Oxytocin is involved in labor and lactation, not maintaining the endometrial lining. Progesterone (from corpus luteum) maintains the lining, so A is incorrect.
• Option B: Follicle - stimulating hormone (FSH) stimulates follicle development, and it is the corpus luteum (not follicles directly) that produces progesterone after ovulation. Also, FSH doesn't directly lead to maintaining the endometrial lining for implantation, so B is incorrect.
• Option C: Gonadotropin - releasing hormone (GnRH) from the hypothalamus stimulates the pituitary to release FSH and LH, but GnRH itself does not maintain the endometrial lining. The maintenance is done by progesterone, so C is incorrect.
• Option D: After fertilization, the embryo's surrounding membrane (chorion) secretes human chorionic gonadotropin (hCG). hCG prevents the corpus luteum from disintegrating. The corpus luteum then continues to secrete progesterone, which maintains the endometrial lining so that the fertilized egg can implant. This is correct.
• Option E: The developing embryo does not prevent progesterone production after corpus luteum breakdown. In fact, hCG prevents corpus luteum breakdown so that progesterone production (from corpus luteum) can continue. Without progesterone, the endometrial lining would shed, so E is incorrect.

Answer:

D. The membrane surrounding the embryo secretes human chorionic gonadotropin, which prevents the corpus luteum from disintegrating.