CNS
Macroglia: Derived from ectoderm of neural tube
Astrocytes
- Function
- Physical support, repair, removal of excess neurotransmitter, component of blood-brain barrier, glycogen fuel reserve buffer. Reactive gliosis in response to neural injury.
- Types
- Protoplasmic
- Fibrous
- Largest and most abundant glial cell in CNS.
- Derived from neuroectoderm.
- GFAP ⊕
Oligodendrocytes
- Myelinated axons of neurons in CNS.
- Each oligodendrocyte can myelinate many axons (∼30).
- Predominant type of glial cell in white matter
- Derived from neuroectoderm.
- "Fried egg" appearance histologically.
- Clinical
- Injured in
- Multiple sclerosis
- Progressive multifocal leukoencephalopathy (PML)
- Leukodystrophies
Microglia
- Derived from mesoderm
- Phagocytes in CNS
- Phagocytic scavenger cells of CNS.
- Activation in response to tissue damage → release of inflammatory mediators (e.g., nitric oxide, glutamate).
- Not readily discernible by Nissl stain.
- HIV-infected microglia fuse to form multinucleated giant cells in CNS in HIV-associated dementia.
Ependymal cells
- Derived from neuroectoderm.
- Line the ventricular system and forms blood CSF barrier.
- Types:
- Ependymyocytes
- Choroid epithelial cells
- Specialized ependymal cells (choroid plexus) produce CSF.
- Tanycytes
- Ciliated simple columnar glial cells lining ventricles and central canal of spinal cord.
- Apical surfaces are covered with cilia (which circulate CSF) and microvilli (which help with CSF absorption).
PNS (both are derived from neural crest)
Schwann cells
- Form myelin sheath in PNS.
- Promote axonal regeneration.
- Derived from neural crest.
- Each "Schwone" cell myelinates only 1 PNS axon.
- Clinical
- Injured in Guillain-Barré syndrome.
- Schwann cell marker: S100.
Capsular cells (also called satellite cells or capsular gliocytes)
- Support and nourish ganglia.
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