In other regions, what we have traditionally called ependyal cells may in fact represent a population of neural stem cells. The result is a barrier limiting access to the interstitial space of the brain from without or within. Recall that in peripheral nerves, a combination of tight junctions between endothelial cells of penetrating capillaries and tight junctions between perineurial fibroblasts surrounding the nerve forms a similar barrier. Astrocytes Astrocytes are star-shaped cells with radiating processes. Other processes extend to the surfaces of the CNS where they form similar expansions that together constitute the outer boundary of the CNS proper.
Astrocytes have numerous filaments within their cell bodies and processes.
These 8-9 nm intermediate filaments typically form closely packed bundles. They can be selectively stained by labeled antibody against glial fibrillary acidic protein , their specific marker protein. Oligodendrocytes Oligodendrocytes have essentially spherical cell bodies from which radiate delicate processes each of which may spin out a segment of myelin. In Nissl preparations, their nuclei are smaller, rounder, and more heterochromatic than astrocytic nuclei. They commonly occur associated with myelinated nerve fibers or as satellite cells in close association with neuronal cell bodies.