Ventricles of the brain

The ventricles of the brain are a communicating network of cavities filled with cerebrospinal fluid (CSF) and located within the brain parenchyma. The ventricular system is composed of 2 lateral ventricles, the third ventricle, the cerebral aqueduct, and the fourth ventricle:

• The two lateral ventricles are the largest of these spaces, one within each of the cerebral hemispheres). The ventral surface of lateral ventricles is defined by the basal ganglia, their dorsal surface by the corpus callosum, and their medial surface by the septum pellucidum.

• The third ventricle forms a narrow midline space between the right and left thalamus, and communicates with the lateral ventricles through a small opening, the interventricular foramen located at the anterior end of the third ventricle. The third ventricle is continuous caudally with the cerebral aqueduct.

• The cerebral aqueduct (aqueduct of midbrain) runs though the midbrain and opens into the fourth ventricle, a larger space located in the dorsal pons and medulla. The fourth ventricle narrows caudally and forms the central canal of the spinal cord.

The presence of ventricular spaces in the various subdivisions of the brain reflects the fact that the ventricles are the adult derivatives of the open space or lumen of the embryonic neural tube

In ventricle are located the choroid plexuses that produce cerebrospinal fluid (CSF), which fills the ventricles and subarachnoid space, following a cycle of constant production and reabsorption. The cerebrospinal fluid percolates through the ventricular system and flows into the subarachnoid space through perforations in the thin covering of the fourth ventricle; it is eventually absorbed by specialized structures called arachnoid villi or granulations, and returned to the venous circulation.