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Nji Gerald Nde

Is the blastocyst a coeloblastula?

Donna Baker  Follow

This is a bit tricky.

The blastocoel in e.g. amphibians separates ectoderm from endoderm and prevents cells of the blastocoel roof from inductive influence of vegetal cells. If you cut out the marginal zone and squish the roof onto vegetal cells, you will end up with mesoderm only:Late amphibian blastula

Blastocoel is not homologous to blastocystic cavity. One could consider a tiny space between epiblast and hypoblast during gastrulation as a homologue of blastocoel, this however does not appear in mice. Blastocystic cavity forms at 32-cell stage thanks to Na+/K+ pumps as well as aquaporins. The inner cell mass is a mixture of cells expressing Gata6 and Nanog, which will form hypoblast and epiblast respectively.

But worry not, many people still call that cavity a blastocoel, in fact, I've seen it happen on Wikipedia. Anyway, I'd still recommend using separate terms for coeloblastula and blastocyst due to the non-homologous nature of blastocystic cavity and the blastocoel.

E vs. H

My sources:

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