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Pronunciation: trof'o-blast, tro'fo-blast

Definition: The mesectodermal cell layer covering the blastocyst that erodes the uterine mucosa and through which the embryo receives nourishment from the mother; the cells do not enter into the formation of the embryo itself but contribute to formation of the placenta. The trophoblast develops processes that later receive a core of vascular mesoderm and are then known as the chorionic villi; the trophoblast soon becomes two layered, differentiating into the syncytiotrophoblast, an outer layer consisting of a multinucleated protoplasmic mass (syncytium), and the cytotrophoblast, the inner layer next to the mesoderm in which the cells retain their membranes.

Synonym(s): chorionic ectoderm

[tropho- + G. blastos, germ]

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© Copyright 2017 Wolters Kluwer. All Rights Reserved. Review Date: Sep 19, 2016.