The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Coelenterates or cnidarians (including jellyfish and corals) and Platyhelminthes (flatworms).
In cnidarians, the gastrovascular system is also known as the coelenteron, and is commonly known as a "blind gut" or "blind sac", since food enters and waste exits through the same orifice.
Extracellular digestion takes place within the central cavity of the sac-like body.
This cavity has only one opening to the outside which, in most cnidarians, is surrounded by tentacles for capturing prey.
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