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Junction area of trophoblast and zona pellucida

Very high power TEM of a portion of the junction area of trophoblast and zona pellucida of a stage 3 embryo in vitro, 145-170 hours post-insemination (original magnification x34,200). The plasma membrane specializations in the trophoblast distinguish it from the inner cell mass (embryoblast). Highly developed microvilli and complex intercellular junctions give the trophoblast the appearance of specialized epithelium. Microvilli are most numerous on the outer surface of the trophoblast where they project toward the zona pellucida.

Mv = microvilli
Ly = lysosome
ZP = zona pellucida

From: Lopata et al., 1982. Reproduced with permission of the publisher, John Wiley & Sons.


Keywords: inner cell mass (embryoblast), junction area of trophoblast and zona pellucida, lysosome(s), microvilli, trophoblast, zona pellucida


Source: The Virtual Human Embryo.