In the brain, there are cavities in which there is no tissue, but cerebrospinal fluid. These are called ventricles. These ventricles are connected to the spinal cord and to each other. There are four ventricles:

• The lateral ventricles (ventricles 1 and 2) are the largest and are located in the inner part of the cerebral hemispheres of the cortex. They are connected to the 3rd ventricle.
• The 3rd ventricle is located on the midline of the brain and below the lateral ventricles. This ventricle is connected to the 4th ventricle through a narrow canal called the cerebral aqueduct.
• The 4th ventricle is located in the corner between the brainstem and the cerebellum, below the 3rd ventricle.

Cerebrospinal fluid is produced in the 1st, 2nd, and 3rd ventricles. Because the brain has no skeleton, this fluid is needed to give it strength and stability. The brain floats in this fluid and this ensures that the pressure on it is evenly distributed. Cerebrospinal fluid also protects the brain and spinal cord from shock and during violent acceleration or braking, such as in a head-on collision. Thus, the cerebrospinal fluid acts as a protective layer between the brain and the skull and serves as a kind of cushion. Through the roof of the 4th ventricle, cerebrospinal fluid escapes into the space between the brain and skull. The cerebrospinal fluid also ensures the supply of nutrients and the removal of waste products.

Fact

The size of the ventricles can be clearly observed on MRI scans. This is important information because enlarged ventricles indicate brain atrophy. That is, as the brain shrinks (atrophies), the ventricles increase in size. This is a normal process that occurs during aging. However, it can also indicate a brain disorder.

Author: Bart Aben (translated by Melanie Smekal)