Glossary term:

Pleura

A two-layered membrane that lines the inside of the chest and covers the surfaces of the lungs. The cavity between the two layers (known as the pleural cavity) is a potential vacuum such that, when the chest wall expands with breathing, the lungs are forced to do so as well, thereby drawing air into them. The pleural cavity is sometimes used by neurosurgeons as a potential receptacle for receiving cerebrospinal fluid from the ventricles of the brain, or for receiving fluid from a syringomyelia cavity.