Amniocyte

An amniocyte (literally "lamb cell") is a cell of a fetus that is suspended in the amniotic fluid. They come from multiple tissues: the umbilical cord, fetal urinary tract, inner amniotic surface, and fetal skin. They are formed through a process of cellular differentiation and shedding from the embryo and placenta. The embryoblast divides into two layers, the epiblast and hypoblast. Cells from the epiblast and trophoblastic cells form the amniotic cavity and amniotic epithelium. Amniocytes formed during gastrulation go through a process of epithelial to mesenchymal transition (EMT) and ingression of epiblast cells at the primitive streak. The primitive streak is formed at the posterior region of the epiblast. The epiblast cells at the primitive streak then go through EMT, losing the epithelial characteristics and becoming more mesenchymal. These cells then ingress into the embryo and form the germ layers, endoderm, mesoderm, and ectoderm. The cells near the top of the epiblast contribute to the amniotic ectoderm, which then forms the amniotic cavity. The lower cells then form a major part of the three germ layers.