The ventricles of the brain are a network of cavities filled with cerebrospinal fluid (CSF) and located within the brain parenchyma. They are structures that produce, transport, and remove cerebrospinal fluid, which bathes the central nervous system. The ventricular system is composed of four ventricles: the right and left lateral ventricles, the third ventricle, and the fourth ventricle. The lateral ventricles are located within their respective hemispheres of the cerebrum and have "horns" that project into the frontal, occipital, and temporal lobes. The third ventricle is situated between the right and left thalamus and is connected to the lateral ventricles by the foramen of Monro. The fourth ventricle is a broad, tent-like cavity of the hindbrain filled with CSF and is bounded anteriorly by the pons and cranial half of the medulla and posteriorly by the cerebellum. The ventricles are lined by ependymal cells, which form a structure called the choroid plexus, where CSF is produced. The main role of the ventricles is the production and distribution of cerebrospinal fluid.