Many animals have spaces or compartments in their body. These spaces or compartments are called body cavity. They are there for organs, or other structures. Sometimes, there is a space between two organs. This space is known as potential body cavity. Potential body cavities usually contain fluid. In the human body, there is a large body cavity on the side of the belly, and another on the side of the back. The one on the side of the belly is called ventral body cavity, the one on the back dorsal body cavity.