High power TEM of a hatching stage 3 embryo in vitro showing the hatching point (original magnification x5,100). Notice the zona-breaker cells (ZBC) on either side of the opening (O) in the zona pellucida (ZP) and dark tonofilaments (arrow) in the bend of one of the cells.
BC = blastocystic cavity (blastocoele)
From: Sathananthan et al., 2003. Printed from Reproductive Biomedicine Online.
Source: The Virtual Human Embryo.