How many ventricles are in the human brain?

The human brain has four ventricles: two lateral ventricles, the third ventricle, and the fourth ventricle.

These interconnected, fluid-filled spaces form part of the brain’s ventricular system. They contain cerebrospinal fluid, which cushions the brain and spinal cord, helps regulate pressure, and transports nutrients and waste products. The two lateral ventricles are the largest and lie within the cerebral hemispheres.

Cerebrospinal fluid flows from the lateral ventricles through the interventricular foramina into the third ventricle. It then passes through the cerebral aqueduct to the fourth ventricle before reaching the space around the brain and spinal cord. The cerebral aqueduct connects the third and fourth ventricles and is a narrow channel in the midbrain.

A common mix-up is counting the lateral ventricles as one cavity. They are a paired set, so they count separately, giving a total of four ventricles in the standard adult human brain.