The ependymal cells, or ependym, are often counted in the glial tissue and form the wall layer in the central canal of the spinal cord and in the ventricular system of the brain. The ependyme can be said to be the CNS's most original cell type; It is from the so-called ependymal layer that both neurons and glial cells are formed during fetal development.
Recent evidence suggests that some ependymal cells, and/or cells hidden among the ependymal cells, in the adult brain retain the ability to divide and develop into neurons and glial cells. These cells are called stem cells.
Transformed ependymal cells, choroid plexus cells, form the cells in the blood vessel braids that produce cerebrospinal fluid (liquor cerebrospinalis).