Medicine and Health related Information

Blastocyst is a spherical cyst lined by flattened trophoblastic cells and inside it there is a mass of cells, the INNER CELL MASS, attached eccentrically to the trophoblast. Further changes are as follows:-

a) Some cells of the inner cell mass diffrentiate into flattened cells that to line its free surface. These constitute the ENDODERM- the FIRST GERM LAYER to be formed.

b) The remaining cells of inner cell mass become columnar cells from the SECOND GERM LAYER- ECTODERM. The embryo is in the form of a disc with 2 layers.

c) A space appears between the ectoderm and the trophoblast, this is the “AMNIOTIC CAVITY” which is filled by amniotic fluid or “LIQUOR AMNEU”. The roof of this cavity is formed by amniogenic cells derived from trophoblast and the floor from ectoderm.

d) “PRIMARY YOLK SAC” a cavity is developed from the flattened cells arising from the endoderm or from trophoblast which spread and line the inside of the blastocystic cavity by the cells of endodermal origin.