Question

What is blastocoel in mammalian development ? What does it signify from the point of view of phylogeny?

Answer 1

A blastocoel is a fluid-filled cavity that forms in the animal hemisphere of early mammalian embryos. A blastocoel is also termed the blastocyst cavity is the name given to the fluid-filled cavity of the blastula (blastocyst) that results from cleavage of the oocyte (ovum) after fertilization. It forms during embryogenesis.

The formation of this blastocoel begins when the early dividing cells of the recently fertilized egg begin to differentiate. This is when they become specialized, as they move around and start to form a new space where there used to be solid cells. These changes, and the presence of the blastocoel, mark the blastula stage of development.