Cleavage division brings about a considerable increase in the mass of protoplasm with each cleavage division, the resultant blastomeres increase in size. During cleavage, at celled stage, a solid ball of cells called morula (as it look like mulberry) is formed. In cleavage, there is increased mobility of protoplasm. The blastomeres in the blastocyst get arranged into outer layer called trophoblast and an inner group of cells attached to trophoblast called trophoblast and an inner group of cells attached to trophoblast called the inner cell mass.

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