What is the role of the allantois in embryonic development?

The allantois plays a crucial role in embryonic development by serving primarily as a storage site for waste products produced by the developing embryo. As the embryo grows, it generates metabolic waste that needs to be dealt with to maintain a healthy environment for development. The allantois collects this waste, preventing it from affecting the embryo negatively.

In many vertebrates, particularly in birds and reptiles, the allantois also functions in gas exchange and can contribute to the formation of the umbilical cord in mammals, linking the embryo to the placenta for nutrient and waste exchange. However, its central and defining function remains related to waste storage in the context of embryonic development, making it vital for the embryo's health and development. Other roles related to support, feeding, or oxygen supply, while important, do not pertain specifically to the allantois.