An extraembryonic membrane is one of the membranes which assist in the development of the embryo. Such membranes occur in a range of animals from humans to insects. They originate from the embryo, but are not considered part of it. They typically perform roles in nutrition, gas exchange, and waste removal. The extraembryonic membranes in insects include a Serous membrane originating from blastoderm cells, an amnion or amniotic cavity whose expression is controlled by the Zerknüllt gene, and a yolk sac.