Endometrium is necessary for implantation of blastocyst.
Reason: In the absence of fertilization, the corpus luteum degenerates that causes disintegration of endometrium.
A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is NOT the correct explanation of A
C
A is true but R is false
D
A is false but R is true
The answer is B.
Solution
Both are true, but the corpus luteum degeneration does not explain why the endometrium is needed for implantation.
Both assertion and reason are correct but reason is not the correct explanation why endometrium is necessary for implantation of blastocyst. The attachment of a blastocyst to the endometrium is called the implantation. It occurs about 6 days after fertilisation. The endometrium is necessary for implantation as it serves as a key place not only for supporting foetal growth through supplementation of oxygen and nutrients but also for protecting the embryo and later the foetus from microbial invasion during pregnancy. If fertilisation does not occur, the levels of progesterone and estrogens decline due to degeneration of the corpus luteum. Withdrawal of progesterone and estrogens causes disintegration of the endometrium leading to menstruation.
Conceptendometrium and implantation
Human Reproduction in past papers
116 questions from this chapter have appeared across 27 exam years.
