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The trophoblast (from Greek trephein: to feed; and blastos: germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. [ 1 ] They provide nutrients to the embryo and develop into a large part of the placenta .
The epiblast gives rise to the three germ layers of the developing embryo during gastrulation (endoderm, mesoderm, and ectoderm). The trophoblast is a layer of cells forming the outer ring of the blastocyst that combines with the maternal endometrium to form the placenta. Trophoblast cells also secrete factors to make the blastocoel. [25]
"Cytotrophoblast" is the name given to both the inner layer of the trophoblast (also called layer of Langhans) or the cells that live there.It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo.
The trophoblast will also develop two sub-layers: the cytotrophoblast, which is in front of the syncytiotrophoblast, which in turn lies within the endometrium. [10] Next, another layer called the exocoelomic membrane or Heuser's membrane will appear and surround the cytotrophoblast, as well as the primitive yolk sac. [11]
Image showing trophoblast differentiated into the two layers of cytotrophoblast and syncytiotrophoblast during implantation. It is the outer layer of the trophoblasts and actively invades the uterine wall, during implantation, rupturing maternal capillaries and thus establishing an interface between maternal blood and embryonic extracellular fluid, facilitating passive exchange of material ...
Before gastrulation, the cells of the trophoblast become differentiated into two layers: The outer layer forms a syncytium (i.e., a layer of protoplasm studded with nuclei, but showing no evidence of subdivision into cells), termed the syncytiotrophoblast, while the inner layer, the cytotrophoblast, consists of well
The fetal membranes are derived from the trophoblast layer (outer layer of cells) of the implanting blastocyst. [3] The trophoblast layer differentiates into amnion and the chorion, which then comprise the fetal membranes. [4] The amnion is the innermost layer and, therefore, contacts the amniotic fluid, the fetus and the umbilical cord. [5]
Cells take on a columnar appearance in the process as they continue to lengthen and narrow. The ends of the neural plate, known as the neural folds, push the ends of the plate up and together, folding into the neural tube, a structure critical to brain and spinal cord development. This process as a whole is termed primary neurulation. [1]