The CSF drains into the third ventricle from the lateral ventricles by way of the interventricular foramena. The fourth ventricle is a small cavity behind the pons and the upper medulla and anterior to the cerebellum. The third ventricle is connected to the fourth ventricle by way of the tubelike cerebral aqueduct. CSF escapes into the subarchnoid space through small openings in the roof of the fourth ventricle. The CSF empties into the fourth ventricle from the third ventricle through the cerebral aqueduct.
Choroid plexuses are a network of vascular capillaries.
CSF fills the ventricles and the subarachnoid cavities of the brain and spinal cord. CSF, a clear and thin fluid, fills the subarachnoid space and the cavities of the ventricles and their branches. It is reabsorbed into the venous blood vessels located within the dura mater. The adult brain contains between 100 and 150 mL of CSF and this entire quantity is replaced three times a day. The CSF in the subarchnoid space of the brain and spinal cord also function as a shock absorber.