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Delayed release of cortical granules into the subzonal space

Very high power TEM of a stage 1a embryo in vitro showing delayed release of cortical granules into the subzonal space, 60 hours post-insemination (original magnification x66,290). Three cortical granules are evident releasing their content by exocytosis into the subzonal space (SS). Collections of diffusing cortical granules (arrowhead) are interacting with the zona pellucida (Z). In the area of exocytosis the cell membrane is dense and striated. A pinocytotic caveolus (Ca) is being formed within the cell membrane, where a cortical granule is degranulating.

From: Sathananthan and Trounson, 1982. Reproduced with permission of the publisher, John Wiley & Sons.

Keywords: cell membrane, cortical granule(s), exocytosis, pinocytotic caveolus, subzonal space, zona pellucida

Source: The Virtual Human Embryo.