User:Croan2019/Germ layer

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Gastrulation occurs in reference to the primary body axis. Germ layer formation is linked to the primary body axis as well, however it is less reliant on it than gastrulation is. Hydractinia shows that germ layer formation that transpires as a mixed delamination.

In mice, germ layer differentiation is controlled by two transcription factors: Sox2 and Oct4 proteins. These transcription factors cause the pluripotent mouse embryonic stem cells to select a germ layer fate. Sox2 promotes ectodermal differentiation, while Oct4 promotes mesendodermal differentiation. Each gene inhibits what the other promotes. Amounts of each protein are are different throughout the genome, causing the embryonic stem cells to select their fate.

During gastrulation, some of the cells migrating inward contribute to the mesoderm, an additional layer between the endoderm and the ectoderm.

Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions protects them from shocks.