Explanation:
The floor of the amniotic cavity is formed by the embryonic disc, which is composed of a layer of prismatic cells and the embryonic ectoderm. ... In humans, the formation of the embryonic disc occurs after implantation and prior to embryonic folding (between about day 14 to day 21 post-fertilization).
The embryonic disc forms the floor of the amniotic cavity. It is composed of a layer of cells – the embryonic ectoderm, derived from the inner cell mass and lying in apposition with the endoderm.
