Glial cells or neuroglia are cells in the central nervous system that produce myelin, destroy pathogens and dead tissue, and maintain nourishment and oxygen to the tissue. They provide support and protection for neurons. Once thought to have no function in the transmission of information within the brain, it has recently become clear that they are key to several autonomous functions, such as breathing. They are key to the development and repair of the brain throughout a person's lifetime. They make up about half the mass and number of cells in the central nervous system, although they are smaller than neurons.
Glial cells tend to specialize in providing either physical support or nourishment to brain tissues. Unlike neurons, they maintain the ability to replicate and divide well into adulthood.