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.
Cross-section showing cavities in the human body, the dorsal and ventral body cavities labelled.
The membranes that surround the central nervous system organs (the brain and the spinal cord, in the cranial and spinal cavities are the three meninges. The differently lined spaces contain different types of fluid. In the meninges for example the fluid is cerebrospinal fluid; in the abdominal cavity the fluid contained in the peritoneum is a serous fluid.