Blastocyst(redirected from blastodermic vesicle)
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blastodermic sac, a stage in the development of mammal embryos, including humans, that arises as a result of cleavage of the fertilized ovum. The blastocyst is a hollow sac. An aggregate of cells—a node, analogous to the blastula of other animals—is found on one side of it. The outer wall of the blastocyst forms the trophoblast.