Given below are two statements. One is labelled as Assertion (A) and the other is labelled as reason (R).
Assertion (A): Implantation in uterus occurs when the trophoblast is attached to endometrium.
Reason (R): After implantation, finger like projections called chorionic villi appear on the trophoblast
In the light of the given statements, choose the correct answer from the options given.

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Both (A) and (R) are true and (R) is the correct explanation of (A)

Both (A) and (R) are true but (R) is not the correct explanation of (A)

(A) is true but (R) is false

Both (A) and (R) are false

answer is B.

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Detailed Solution

The trophoblast layer gets attached to the endometrium and the inner cell mass gets differentiated as the embryo. After attachment, the uterine cells divide rapidly and covers the blastocyst. As a result, the blastocyst becomes embedded in the endometrium of the uterus. This is called implantation and it leads to pregnancy.

After implantation, finger-like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood. The chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between developing embryo (foetus) and maternal body called placenta.

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