The placenta is a temporary organ that surrounds the fetus during gestation. The placenta allows for transport of gases and nutrients, and also provides other metabolic and endocrine functions. The amniotic membrane (AM) is an avascular membranous sac that is filled with amniotic fluid. The AM is the innermost membrane surrounding a fetus in the amniotic cavity. AM also forms the outer layer of the umbilical cord, which connects the placenta to the fetus and transports oxygen to the fetus. Wharton's jelly, a specialized gelatinous connective tissue material, surrounds the umbilical cord to protect it from damage during fetal movement and development. The AM tissue consists of an epithelial layer and a subjacent avascular stromal layer. The chorion surrounds the amniotic membrane. The chorion consists of two layers: an outer layer formed by the trophoblast, and an inner layer formed by the somatic mesoderm; the amnion is in contact with the latter. 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.
USPTO Backgrounds
USPTO Backgrounds