Gastrulation After blastulation, the single-layered blastula expands and reorganizes into multiple layers, a gastrula (seen in the figure to the right). Reptiles, birds and mammals are triploblastic organisms, meaning the gastrula comprises three germ layers; the endoderm (inner layer), mesoderm (middle layer), and ectoderm (outer layer). As seen in the figure below, each germ layer will become multi-potent stem cells that can become a specific tissue depending on the germ layer and is what happens in humans. This differentiation of germ layers differs slightly, because not all of the organs and tissues below are in all organisms, but corresponding body systems can be substituted in place of these.
Gastrulation After blastulation the single-layered blastula expands and reorganizes into multiple layers a gastrula (seen in the figure to the right) Reptiles birds and mammals are triploblastic organisms meaning the gastrula comprises three germ layers; the endoderm (inner layer) mesoderm (middle layer) and ectoderm (outer layer) As seen in the figure below each germ layer will become multi-potent stem cells that can become a specific tissue depending on the germ layer and is what happens in humans This differentiation of germ layers differs slightly because not all of the organs and tissues below are in all organisms but corresponding body systems can be substituted in place of these