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Pronunciation: kom-pak'shun

Definition: The process following the third cleavage division of the zygote during which the blastomeres maximize their contact with each other by polarization and adhesion, forming a compact ball that is held together by tight junctions; compaction segregates the inner cells of the blastocyst that form the embryo from the outer cells that form the fetal part of the placenta.

[L. compactio, fr. com-pingo, pp. com-pactus, to press together]

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.