Gastrovascular Cavity: As the name implies, this has a role in both the distribution of particles and nutrients to all areas of the body as well as having a role in digestion. Organisms that belong to 2 main phyla – the Platyhelminthes and the Cnidaria – have gastrovascular cavities. The cnidarians that are symmetrical have a body that is sac-like in 2 layers that are distinct – the epidermis and gastrodermis – with a jelly type layer called the mesoglea in between. Digestion that is extra cellular begins within the center cavity of the body that is sac-like. This cavity or hollow has only 1 means leading outside and in the majority of cnidarians that opening is surrounded by tentacles that serve to seize prey. An example is the digestion in hydra happens in the gastrovascular cavity.
Those organisms having a gastrovascular cavity include: jellyfish, sea anemones, corals, sea pen and flatworms.