Trophoblast

The trophoblast is the outer cell layer of a blastocyst and connects it to the uterine wall. It forms at the 5th to the 12th day after fertilization of blastomeres differs by enzymes, the uterine lining and can thus be deposited on it.

By dissolving the mucosal cells of the uterus of the seed is fed the first time. During this stage, the trophoblast grows with the help of his Synzytiotrophoblastenanteils invasive in the endometrium on by the relevant cells lose their boundaries, while irregular trabeculae networked and form lacunae ( lakunäres stage, 8th - 9th day). The necessary for the operation of the cytotrophoblast cell material supplies, this is the proportion lying around the embryoblasts of the trophoblast.

From this stage are now entering the first zottenartigen structure in appearance, it is called the Primärzotten or villi. In this penetrating from day 12 a cytotrophoblast cells, the Synzytiotrophoblastanteil is thinned and only forms a thin surface layer. From this stage is called the Sekundärzotten. From about the 20th day breaks extraembryonic mesoderm in the Sekundärzotten ago, in which form blood vessels, found that connection to the vessels of the body stalk, and so make the final vascular supply of the embryo.

In the further course of this contact on the so-called tertiary villi Hofbauer cells ( macrophages) that stimulate Zottenwachstum addition and phagocytose foreign bodies. This now growing Zottenbäume together with residuierenden maternal shares the placenta, which takes care of all vital functions for those resulting from the germinal disc embryo.

Trophoblasts have no MHC class 1 antigens.