Definition: A system of fluid-filled open spaces in the brain. There are four ventricles: two lateral ventricles, one third ventricle and one fourth ventricle. The fluid that fills these ventricles is called "cerebral spinal fluid" (CSF).
The lateral ventricles, which are located on each side of the brain, are connected directly with the third ventricle, which lies at the center of the brain. The latter connects with the fourth ventricle through a small passage called the "aqueduct of Silvius." The fourth ventricle, which is located in the back of the brain, is connected with the central canal of the spinal cord.
Also Known As: ventricular system
