Formation of the Blastocyst
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Compaction: Blastomeres clump together; the amount of cytoplasm is reduced
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Adhesion: E-cadherin gene is expressed; these proteins facilitate intercellular
adhesion and communication
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Zona pellucida is shed, allowing for cell growth and for uterine fluid
to infiltrate
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A fluid-filled cavity (blastocoele) forms in the center, pushing cells
to the periphery
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The outer cell layer, the trophoblast ("tropho" - to nourish), may have
a nutritive role as the future embryonic part of the placenta
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The inner cell mass, the future embryo, forms as a ball of cells on one
side of the spherical blastocyst
