Glial cells: astrocytes, oligodendrocytes, microglia, Schwann cells !
- Cell
Glial cells support, insulate, feed and defend neurons; they outnumber neurons and, unlike them, can divide.
Updated 2026-11-01
See it in 3D: White matter · Spinal cord · Dorsal root ganglia
What it is
Neuroglia are the non-signalling cells of nervous tissue. The central nervous system has astrocytes, oligodendrocytes, microglia and ependymal cells; the peripheral nervous system has Schwann cells and satellite cells. They make myelin, control the chemical environment of neurons, help form the blood–brain barrier, clean up debris and form scars. Most brain tumours of adults arise from glia.
Structure
- On H&E mostly only glial nuclei are seen: astrocytes have larger oval pale nuclei, oligodendrocytes small round dark nuclei with a clear halo, microglia small elongated rod-shaped nuclei.
- Astrocyte processes need GFAP immunostaining or silver stains to be seen.
- Myelin is many layers of glial cell membrane wrapped around the axon; it is rich in lipid, so it is pale with H&E and dark with Luxol fast blue or osmium.
- Nodes of Ranvier are the gaps between myelin segments where sodium channels cluster, allowing saltatory conduction.
Glial cells: where they are and what they do
| Cell | System | Origin | Job | When it fails |
|---|---|---|---|---|
| Astrocyte | CNS | Neuroectoderm | Feet on capillaries (blood–brain barrier), buffers potassium, recycles glutamate, forms the glial scar; marker GFAP | Glioblastoma and other astrocytomas; reactive gliosis after injury |
| Oligodendrocyte | CNS | Neuroectoderm | Myelinates segments of many axons at once; 'fried egg' cells with a clear halo in white matter | Multiple sclerosis; leukodystrophies; PML (JC virus) |
| Microglia | CNS | Mesoderm (yolk-sac macrophage lineage) | Resident phagocytes; activate after injury and infection | HIV infects them (multinucleated giant cells) |
| Ependymal cell | CNS | Neuroectoderm | Ciliated cuboidal-columnar lining of ventricles and central canal; with the choroid plexus, CSF production and flow | Ependymoma, often in the fourth ventricle of children |
| Schwann cell | PNS | Neural crest | Myelinates one internode of one axon; also wraps unmyelinated axons; guides regeneration | Guillain-Barré syndrome; schwannoma (vestibular schwannoma) |
| Satellite cell | PNS | Neural crest | Surrounds neuron cell bodies in sensory and autonomic ganglia | Site of latent herpes and varicella-zoster virus in sensory ganglia (in neurons they surround) |
Clinical notes
- Multiple sclerosis: autoimmune destruction of CNS myelin and oligodendrocytes gives sharply bordered plaques of demyelination in white matter, often around the ventricles.
- Guillain-Barré syndrome: autoimmune attack on peripheral myelin (Schwann cells), often after an infection, causes ascending weakness.
- Glioblastoma, the most aggressive astrocytic tumour, shows necrosis with pseudopalisading tumour cells and vascular proliferation.
- Reactive astrocytes form a glial scar that seals CNS injuries but blocks axon regrowth.
Test yourself
Think of the answer, then tap the question to see it.
Which glial cell makes myelin in the CNS, and which in the PNS?
Oligodendrocytes in the CNS, each covering many axons; Schwann cells in the PNS, each covering one segment of one axon.
Which glial cell is not derived from neuroectoderm or neural crest?
Microglia, which come from mesoderm (the yolk-sac macrophage lineage) and act as resident phagocytes.
Which immunohistochemical marker identifies astrocytes and astrocytic tumours?
Glial fibrillary acidic protein (GFAP).
Why is Guillain-Barré syndrome a peripheral and multiple sclerosis a central demyelinating disease?
Guillain-Barré targets Schwann-cell myelin of peripheral nerves; multiple sclerosis targets oligodendrocyte myelin of the brain and spinal cord.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- The neuron and synapse
- Peripheral nerve: endoneurium, perineurium, epineurium; myelin
- Gray and white matter, cerebellar cortex, meninges
- Nerve injury and regeneration (Wallerian degeneration)
Related conditions
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 12.2 Nervous Tissue (OpenStax, 2022); 4.5 Nervous Tissue Mediates Perception and Response (OpenStax, 2022); Multiple Sclerosis (MedlinePlus, U.S. National Library of Medicine, 2025).
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Representative model, for educational purposes only.