The cytotrophoblast is considered to be the trophoblastic stem cell because the layer surrounding the blastocyst remains while daughter cells differentiate and proliferate to function in multiple roles.
12.
In normal early embryonic development, the outer epithelial layer contains cytotrophoblast cells, a stem cell type found in the trophoblast that later differentiates into the fetal placenta.
13.
Data has shown that Mig-7 expression is specific to human embryonic / fetal cytotrophoblast cells and epithelial type cancer cells, while not expressed in normal cells.
14.
At days 11 to 12, there is further delineation of the trophoblastic cells giving rise to a layer of loosely arranged cells that inserts between Heuser s membrane and both syncytiotrophoblast and cytotrophoblast.
15.
Furthermore, as the cytotrophoblast differentiates the expression of HERV-W env mRNA and glycoprotein both increase collinearly suggesting HERV-W env expression is correlated with the fusion and differentiation of cells.
16.
At day 9-10 of embryonic development, cells from the hypoblast begin to migrate to the embryonic pole, forming a layer of cells just beneath the cytotrophoblast, called Heuser's Membrane.
17.
The trophoblast is made up of an internal layer of cubical or prismatic cells, the cytotrophoblast or layer of Langhans, and an external layer of richly nucleated protoplasm devoid of cell boundaries, the syncytiotrophoblast.
18.
Normally the maternal circulation and the fetal circulation are kept from direct contact with each other, with gas and nutrient exchange taking place across a membrane in the placenta made of two layers, the syncytiotrophoblast and the cytotrophoblast.
19.
The extraembryonic coelom divides the extraembryonic mesoderm into two layers : extraembryonic splanchnopleuric mesoderm, which lies adjacent to Heuser's membrane around the outside of the primitive yolk sac, and extraembryonic somatopleuric mesoderm, which lies adjacent to the cytotrophoblast layer of the embryo.
20.
In the first hours after fertilization, this zygote divides into identical totipotent cells, which can later develop into any of the three germ layers of a human ( endoderm, mesoderm, or ectoderm ), into cells of the cytotrophoblast layer or syncytiotrophoblast layer of the placenta.
