Comparison with Amphibian Gastrulation
On comparison of chick gastrulation along with amphibian gastrulation you will find many similarities along with significant differences. Primitive streak is analogous to the blastopore although there is no actual pore. The Hensen's Node presents the dorsal lip and the folds on the lateral sides of primitive groove present the lateral lips. However, there is no ventral lip. As in amphibians, the prechordal endoderm and chorda mesoderm of chick migrate inward by the Hensen's Node (dorsal lip) and the remaining endoderm and mesoderm do so by involution over the lateral folds of the streak (lateral lips). The topographic locations of the presumptive ectodermal, chordarnesodermal; mesodermal and endodermal areas relative to each other in the epiblast are nearly similar as on the surface of amphibian blastula. As in amphibians, the involuting mesodermal and endodermal cells change shape to become bottle cells in the gastrulating chick embryos as well.