The brain ventricles are a system of interconnected cavities located within the brain. They are filled with a clear fluid called cerebrospinal fluid (CSF), which cushions the brain, removes waste, and helps maintain stable pressure. There are four main ventricles: the two lateral ventricles, the third ventricle, and the fourth ventricle. These ventricles play a crucial role in the overall health of the central nervous system. The CSF circulates through the ventricles and around the brain and spinal cord, providing essential nutrients and protection. Any blockage or abnormality in the ventricles can lead to conditions such as hydrocephalus, which requires medical attention.