Question of the day

The placenta is composed of three layers. The innermost placental layer surrounding the fetus is called the amnion. The allantois is the middle layer of the placenta that derived from the embryo; blood vessels originating from the umbilicus traverse this membrane. The outermost layer of the placenta, the chorion, comes into contact with the endometrium; it is composed of two layers of cells - inner cytotrophoblast and outer syncytiotrophoblast.