Question

Given below are two statements with respect to gastrulation:
Statement (I): The cells of epiblast towards the blastocoel contribute in the formation of yolk sac.
Statement (II): The cells of epiblast take part in the formation of third germinal layer, the mesoderm.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

The yolk sac comes from hypoblast cells, while the mesoderm comes from epiblast cells.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
At the start of gastrulation the inner cell mass splits into an upper epiblast and a lower hypoblast.

Step 2: Statement (I)
The hypoblast cells next to the blastocoel spread to line it and form the yolk sac. The epiblast does not form the yolk sac, so Statement (I) is incorrect.

Step 3: Statement (II)
Epiblast cells move inward through the primitive streak and give rise to the mesoderm and endoderm, while those left on the surface form ectoderm. Statement (II) is correct.

Final Answer:
Statement (I) is incorrect but Statement (II) is correct. \[ \boxed{\text{(D) }\text{Statement (I) is incorrect but Statement (II) is correct}} \]