Theiler Stage 7 - Implantation and formation
of Egg Cylinder
Ectoplacental cone appears. Rapid increase in the number of inner
cell mass cells leading to the formation of the epiblast with subsequent
growth to form the egg cylinder. The proximal or visceral cells
(opposite side from the trophoblastic cap) are cuboidal in shape.
Primary endoderm lines the mural trophectoderm.