The trophoblast Trophoblast Cells lining the outside of the blastocyst. After binding to the endometrium, trophoblasts develop into two distinct layers, an inner layer of mononuclear cytotrophoblasts and an outer layer of continuous multinuclear cytoplasm, the syncytiotrophoblasts, which form the early fetal-maternal interface (placenta).
The invasion of a specific type of trophoblast (extravillous trophoblast) into the maternal uterus is a vital stage in the establishment of pregnancy. Failure of the trophoblast to invade sufficiently is important in the development of some cases of pre-eclampsia.
A useful component of current placentation and trophoblast research are a number of trophoblast cell lines that have been derived from a number of different sources including term placenta, choriocarcinomas and transformation of primary isolated cells.
The trophoblast originates from the trophectoderm (see below) and differentiates into multiple specialized trophoblast subpopulations and phenotypes. They either differentiate into polar cells serving typical epithelial functions, or into apolar invasive cells that remodel and adapt the maternal uterine wall to progressing pregnancy.
The initial layer of trophoblast cells, known as the trophectoderm, is contiguous with the embryonic ectoderm. As pregnancy progresses, trophoblasts undergo rapid proliferation and differentiation, forming distinct layers and structures.
The intermediate trophoblast on the villous surface forms trophoblastic columns that anchor the fetal part of placenta to the implantation site. In all other locations, the trophoblast is referred to as extravillous trophoblast and is composed mostly of intermediate trophoblast.
trophoblast: The membrane of cells that forms the wall of a blastocyst during early pregnancy, and also provides nutrients to the embryo and later develops into part of the placenta.
The trophoblast plays an important role later in the development of the placenta or afterbirth. The conceptus makes contact with the uterine lining about the fifth or sixth day after conception.…