Coeloms are important because they allow for the separation and compartmentalization of different biological functions in the body. Animals lacking coelom have to rely on diffusion to transport important nutrients throughout the body.
The coelom usually refers to the main body cavity. It surrounds and contains the digestive tract and helps prevent injury to the digestive organs. Inside the coelom, there is a fluid called coelomic fluid. This fluid allows the internal organs to freely move. It also helps to transport waste, nutrients and gases between several different body parts and organs. Most vertebrates have a coelom and are therefore called 'coelomates.'