TEM of the polar trophoblast region of a stage 3 embryo in vitro, 145-170 hours post-insemination (original magnification x10,800). Where polar trophoblast cells are adjacent to sequestered cells (SC) the microvilli (Mv) are either against the inner surface of the sequestered cells or extend between them toward the zona pellucida.
From: Lopata et al., 1982. Reproduced with permission of the publisher, John Wiley & Sons.
Source: The Virtual Human Embryo.