The Mouth is the Last Thing Produced by Growth of the Archenteron

Question

The mouth is the last thing produced by growth of the archenteron through the sea urchin gastrula.

Accepted Answer

The archenteron, or primitive gut, pushes through the blastopore during gastrulation in sea urchins. The mouth is the last opening formed at the end of this process, as the archenteron continues to elongate and differentiate into the digestive system.