What are the extra-embryonic membranes that surround a fetus?

The extra-embryonic membranes that surround a fetus include the amnion, chorion, allantois, and yolk sac. The amnion forms a protective sac filled with amniotic fluid, providing cushioning. The chorion contributes to the formation of the placenta and facilitates nutrient exchange. The allantois is involved in waste management and gas exchange, while the yolk sac provides early nourishment before placental circulation is established.