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Gastrulation has been studied in many animals, but some models have been used for longer than others. Furthermore, it is easier to study development in animals that develop outside the mother. Model organisms whose gastrulation is understood in the greatest detail include the mollusc, sea urchin, frog, and chicken.
A computational model of Clytia hemisphaerica gastrulation. [4] Red cells depict presumptive endodermal cells, and blue cells depict presumptive ectodermal cells. Changes in the adhesion properties of these cells are the best characterized and understood mechanism of ingression. [3]
The blastula develops into a structure called a gastrula through a process called gastrulation. The gastrula then undergoes further development, including the formation of organs ( organogenesis ). The embryo then transforms into the next stage of development, the nature of which varies among different animal species (examples of possible next ...
This matches with the "flaps-folding-over" model of gut formation, but an alternative view is that the original blastopore migrated forwards to one end of the ancestral organism before deepening to become a blind gut. [1] This is consistent with living Xenacoelomorpha, which are the sister taxon to protostomes and deuterostomes.
Invagination of the archenteron during sea urchin gastrulation. Sea urchin gastrulation is another classic model for invagination in embryology. One of the early gastrulation movements in sea urchins is the invagination of a region of cells at the vegetal side of the embryo (vegetal plate) to become the archenteron, or future gut tube. There ...
Early embryogenesis, showing the cycles of nuclei divisions in the syncytial blastoderm and the morphogenetic movements of gastrulation. Embryogenesis in Drosophila is unique among model organisms in that cleavage occurs in a multinucleate syncytium (strictly a coenocyte). Early on, 256 nuclei migrate to the perimeter of the egg, creating the ...
The primitive node (or primitive knot) is the organizer for gastrulation in most amniote embryos. In birds, it is known as Hensen's node, and in amphibians, it is known as the Spemann-Mangold organizer. It is induced by the Nieuwkoop center in amphibians, or by the posterior marginal zone in amniotes including birds.
It can be seen from the outside as the shrinking of the yolk sac. Near the end of gastrulation, the yolk sac becomes entirely covered by the ectoderm, and the blastopore assumes the shape of a vertical cleavage. The three germ layers form a characteristic shape. The ectoderm is the outermost layer, the mesoderm is the middle one, and the ...