What is the volume of the cerebrospinal fluid (CSF)?

140–150 ml.

Where is CSF produced, and at what rate?

70% of CSF is produced by the choroid plexus of the lateral, third and fourth ventricles. 30% comes directly from the vessels lining the ventricular walls. It is produced at a rate of 0.35 ml/min, or ∼500 ml/day.

Briefly describe the circulation of CSF.

From the lateral ventricle, the CSF flows into the third ventricle through the interventricular foramen of Monro. From here it enters into the fourth ventricle through the aqueduct of Sylvius. Some continue down into the central canal of the spinal cord, but the majority flow into the sub-arachnoid space of the spinal cord via the central foramen of Magendie, or the two lateral foramina of Luschka. After going around the spinal cord, it enters the cranial cavity through the foramen magnum, and flows around the brain within the sub-arachnoid space.

What are the arachnoid villi composed of?

The arachnoid villi are formed from a fusion of arachnoid membrane and the endothelium of the dural venous sinus that it has bulged into.

Where is the CSF finally absorbed?

80% of CSF is absorbed at the arachnoid villi, and 20% is absorbed at the spinal nerve roots.

What structures form the blood-brain barrier (BBB)?

The BBB, which is a histological and physiological boundary between the blood and the CSF, is formed from two types of special anatomical arrangement

Tight junctions in-between the endothelial cells of the cerebral capillaries

Astrocytic foot processes applied to the basal membranes of the cerebral capillaries

What substances can pass through the BBB?

The BBB, which is a histological and physiological…