Question

Termination of gastrulation is indicated by

• A. obliteration of blastocoel
• B. obliteration of archenteron
• C. closure of blastopore
• D. closure of neural tube.

Answer 1

The Correct Option is A

The question asks about the event that indicates the termination of gastrulation. Gastrulation is a crucial phase in embryonic development where the blastula reorganizes into a multilayered structure known as the gastrula. Here is a step-by-step explanation of the process and how to determine the correct answer:

1. Understanding Blastocoel: The blastocoel is a fluid-filled cavity within the blastula. During gastrulation, cells migrate to form different germ layers, and as they do so, the blastocoel is gradually replaced by a new cavity, the archenteron.
2. Understanding Archenteron and Blastopore:
   • The archenteron is the primitive gut formed during gastrulation, which will eventually develop into the digestive tract.
   • The blastopore is the opening of the archenteron to the outside, which becomes the anus in deuterostomes (like humans) and the mouth in protostomes.
3. Termination of Gastrulation:
   • The termination of gastrulation is marked by the completion of cell movement and the formation of the primary gut.
   • During this process, the obliteration of the blastocoel occurs as it is replaced by the archenteron.
4. Analyzing the Options:
   • Obliteration of blastocoel: Correct, as it marks the end of the movement of cells forming the primary layers, hence indicating the end of gastrulation.
   • Obliteration of archenteron: Incorrect, as the archenteron forms and persists to become the gut.
   • Closure of blastopore: Incorrect, the closure indicates later embryonic developments.
   • Closure of neural tube: Incorrect, as it represents a much later stage than gastrulation, involved in neurulation.

Given these considerations, the termination of gastrulation is correctly indicated by the obliteration of the blastocoel, as it marks the successful transition from the blastula to the formation of the trilaminar germ layers. This matches the provided correct answer.