A Reproductive Lexicon


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Cleavage, with regard to the embryo, is a term that refers to the first few mitotic divisions of the pre-implantation embryo. These cell divisions, which begin shortly after fertilization, transform a single cell zygote into a multicellular embryo. Up until the blastocyst stage, the cell divisions serve to increase the embryo’s cell number but do not increase the embryo’s actual size.