What is the foetal part of Choriovitelline placenta (or Yolk-sac placenta) formed of?
It is formed of chorion and yolk sac? Why's the vitelline in the name?
A a foetal portion of Choriovitelline placenta is formed by the chorion. Choriovitelline placenta is a type of placenta in which the yolk sac becomes an intermediary in the fetal-maternal relationship. There the vitelline takes up the whole of the inner embryonic layer and surrounds the embryo. The allantois shrinks.