The fourth ventricle is the diamond shaped cavity in a group of four cavities within the brain. It is the most inferior ventricle. It communicates with the spinal cord through the lateral apertures and the median aperture. Cerebrospinal fluid is formed from choroid plexuses which are located in the ventricles. So the ventricles are filled with cerebrospinal fluid. The fourth ventricle extends from the cerebral aqueduct to the obex.

Ventriculus quartus

Ventriculus quartuus

Quatrième ventricule