High power TEM of the subzonal space of a stage 2, 8-cell embryo in vitro 72 hours post-insemination (original magnification x19,600). One cortical granule (arrowhead) is interacting with the zona pellucida (ZP) which has dense bands.
From: Sathananthan and Trounson, 1982. Reproduced with permission of the publisher, John Wiley & Sons.
Keywords: cortical granule(s), eight-cell embryo, subzonal space, zona pellucida
Source: The Virtual Human Embryo.