Chorion Villous

The fleecy chorion (s.villosum) refers to multicellular metameric formations of mesodermal origin. It includes several types of cells of different morphological forms capable of performing trophic, transport functions and producing mesoderm. This is the first pretern organ that appears in the blastula stage of the embryo. Actually, at the larval stage it is already present in the eel embryo.

In early human embryology, it is known as the grooved chorion because of its specific shape, which it achieves starting from the 4th week of development. At longer periods, the accumulation of amniotic fluid begins, but the contents inside the yolk sac remain in place. As a result, a thin film filled with amniotic cells begins to form. It is formed in the form of a groove between the membrane of the yolk sac and the shiny polyeast layer of the cell cytoplasm that has peeled off above it.