Schwann cells are a vital type of glial cell found in the peripheral nervous system (PNS). Their primary function is to support neurons, and in many cases, to form the myelin sheath around axons.
Function of Schwann Cells
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Myelin Sheath Formation: Myelinating Schwann cells wrap around the axons of motor and sensory neurons, creating a multilayered myelin sheath. This sheath acts as insulation, allowing for faster and more efficient nerve impulse transmission. This is analogous to the insulation around electrical wires. Unlike oligodendrocytes (which perform a similar function in the central nervous system), each Schwann cell myelinates only a single segment of a single axon.
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Neuron Support: Even non-myelinating Schwann cells provide crucial support to neurons. They maintain the health and survival of these neurons.
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Nerve Repair: Schwann cells play a significant role in the repair and regeneration of damaged nerves in the PNS. They guide axon regrowth and promote remyelination after injury. This is a key factor in the recovery from nerve damage in the extremities.
Origin and Development
Schwann cells originate from neural crest cells during embryonic development. This development involves a precise series of steps, ultimately resulting in the mature Schwann cell populations that support the PNS.
Comparison with Oligodendrocytes
While both Schwann cells and oligodendrocytes produce myelin, they differ significantly:
- Location: Schwann cells are in the PNS; oligodendrocytes are in the CNS.
- Myelination: A single Schwann cell myelinates a single segment of one axon, while a single oligodendrocyte can myelinate multiple segments of multiple axons.
Clinical Significance
Schwann cells are involved in various pathological conditions, including:
- Peripheral neuropathies: Diseases affecting the PNS can disrupt Schwann cell function, leading to impaired nerve conduction and symptoms such as numbness, tingling, and weakness.
- Cancer: Schwann cells can be involved in the development of certain types of tumors, such as schwannomas.
