Blastopore is the transitory opening on the surface of gastrula through which the internal cavity archenteron) communicates with the exterior. It is formed by invagination of superficial cells during gastrulation.

Physiology) embryol the opening of the archenteron in the gastrula that develops into the anus of some animals.
blastopore - the opening into the archenteron

Blastopore is the opening of the archenteron.

The blastopore is a crucial feature of early embryonic development in animals. It is the initial opening that forms during gastrulation, a process that establishes the three germ layers (ectoderm, mesoderm, and endoderm) and sets the foundation for the development of various body structures.

1. Gastrulation and germ layer formation:
During gastrulation, a single-layered blastula transforms into a multilayered structure through invagination and inward migration of cells. This process leads to the formation of the three germ layers, which give rise to different tissues and organs in the developing embryo.

2. Formation of the archenteron:
As cells invaginate and migrate, a central cavity called the archenteron is formed. The archenteron will later develop into the digestive tract of the animal. The opening of the archenteron is called the blastopore.

3. Fate of the blastopore:
In deuterostomes (a group of animals that includes vertebrates), the blastopore eventually develops into the anus, while the mouth forms from a secondary opening. This pattern is observed in animals such as humans, birds, and reptiles.

4. Comparison with other options:
a) Coelenteron: The coelenteron refers to the central cavity of coelenterates (e.g., jellyfish), which is not relevant to blastopore development.
b) Coelom: The coelom is the body cavity that forms within the mesoderm. It is not directly related to the blastopore.
c) Blastocoel: The blastocoel is the fluid-filled cavity inside the blastula. It is formed during cleavage and is not the same as the blastopore.

Therefore, the correct answer is option 'D' - archenteron. The blastopore is the opening of the archenteron, which later differentiates into the digestive tract of the developing embryo.