Extraembryonic membranes are specialized structures that develop outside the embryo during early stages of vertebrate development. They play crucial roles in supporting the embryo by providing protection, nutrition, and waste management. The main types of extraembryonic membranes include the amnion, chorion, yolk sac, and allantois. These membranes are essential for the survival of the embryo, especially in amniotes, which include reptiles, birds, and mammals. The amnion surrounds the embryo, creating a fluid-filled cavity that cushions it, while the chorion facilitates gas exchange. The yolk sac provides nutrients, and the allantois helps in waste disposal.