What is the main function of ependymal cells in the CNS?

Ependymal cells are specialized glial cells that line the ventricles of the brain and the central canal of the spinal cord. Their primary function is to produce cerebrospinal fluid (CSF), which is essential for cushioning the brain, providing buoyancy, and serving as a medium for nutrient exchange and waste removal within the central nervous system. The production of CSF is critical for maintaining homeostasis in the CNS, as it helps protect the delicate neural tissues from physical injury and supports proper neuronal function.

While other types of glial cells have distinct functions—such as oligodendrocytes which form the myelin sheath around nerve fibers, microglia that act as immune cells, and astrocytes that assist with neuron signaling—the unique role of ependymal cells in the production of CSF is what primarily defines their purpose in the central nervous system.