Embryo progresses from morula to the blastocyst still within
the zona pellucida (shown in red). There is early evidence of the
3 dpc (range 2-4)
16-40 compacted cells.
All scale bars in microns.
In the blastocyst stage (zona-intact) there is a distinct inner
cell mass and an outer layer of trophectoderm cells. Usually located
in the uterine lumen.