The Coelom is a cavity within the body of all animals higher than the coelenterates and certain primitive worms, formed by the splitting of the embryonic mesoderm into two layers. In mammals it forms the peritoneal, pleural, and pericardial cavities. It is also called abdominal cavity.
The coelom allows for great increases in body size.
The presence or absence of a coelom is important for the classification of animal phyla.
The coelom is a fluid filled cavity that helps absorb shock and provides a hydrostatic skeleton. It also allows organs to grow independently of the body wall.