What are gastrovascular cavities?

Gastrovascular cavities are structures that are found in primitive class of organisms called phyla, which are animals with relatively simple physical structures. Gastrovascular cavities help phyla digest food and further assist with the passage of food through their bodies. These cavities have one opening to the external environment, which allows food and waste to pass through.

The ability of gastrovascular cavities to use a single opening for food ingestion and excretion makes them two-way digestive tracts. This contrasts the digestive system of most organisms, which have mouths on one end of their bodies and an anus on the other. These digestive tracts are referred to as alimentary canals.