What is the name of the brain’s fluid-filled cavity system containing cerebrospinal fluid?

The ventricular system is the brain’s connected set of fluid-filled cavities containing cerebrospinal fluid.

It consists of two lateral ventricles plus the third and fourth ventricles. Narrow channels connect these spaces, allowing cerebrospinal fluid to circulate through the brain and then into the subarachnoid space around the brain and spinal cord.

The fluid is produced mainly by specialized tissue called the choroid plexus. It cushions the central nervous system, helps maintain a stable chemical environment, and provides a route for waste removal and distribution of certain signaling molecules. Cerebrospinal fluid is continuously produced and reabsorbed rather than remaining still inside the cavities.

The ventricular system is different from the subarachnoid space, although both contain cerebrospinal fluid. Blockage of the connecting pathways can cause hydrocephalus, in which fluid accumulates and raises pressure. Enlargement of a ventricle is therefore a clinical finding, not a separate anatomical system.