Gastrulation

Gastrulation
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Gastrulation
Gastrulation is the process by which groups of cells are reorganized to form a new life form, be it in amphibians, birds, reptiles or mammals. Essentially gastrulation is the same across most living organisms. This is because gastrulation is all about the change in motility, adhesion and the shape of cells. Birds’ gastrulation is the most similar to that of mammals. In both, cells move outwards along the primitive groove or streak to form the outer layers of the young one. The uterus has the same function as the shell, which is to protect the cells inside. The chorion, which is useful for gaseous exchange in the eggs, is the equivalent of the placenta in mammals. The allantoic cells, which help in the movement of waste materials, are the equivalent of the umbilical cord in mammals.
Reptiles, birds and mammals are all amniotes. This means that they all employ a series of membranes that are extra-embryonic to assist in embryonic development. They also obviously have amniotic fluids too. Reptile and bird eggs are very similar. Gastrulation in amphibians is similar to the other three though it differs slightly in the details. It starts with a mass of cells called blastomeres (in mammals this is referred to as blastocyst. The outside cells move inwards to form the interior. This triggers ...