The ventricles are shown in blue on the following midsagittal section of the brain. The Ventricles CSF is produced mainly by a structure called the choroid plexus in the lateral, third and fourth ventricles.CSF flows from the lateral ventricle to the third ventricle through the interventricular foramen (also called the foramen of Monro).he third ventricle and fourth ventricle are connected to each other by the cerebral aqueduct (also called the Aqueduct of Sylvius). CSF then flows into the subarachnoid space through the foramina of Luschka (there are two of these) and the foramen of Magendie (only one of these).