Fourth ventricle

The fourth ventricle is located between the pons and medulla. The superior and inferior medullary velum lie dorsally while the rhomboid fossa lies ventrally. The cerebellar peduncles are found on each side. Like the lateral and third ventricles, the fourth ventricle contains a choroid plexus, which produces cerebrospinal fluid (CSF). CSF enters through the cerebral aqueduct and flows out through three possible pathways: via the obex into the central canal, via the median aperture into the cisterna magna, and via the lateral apertures into the cerebellopontine cistern.