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Myelination of Axons by Schwann Cells

  • All axons in the peripheral nervous system are surrounded by Schwann cells, and the cover produced by these cells is often referred to as the sheath of Schwann.
  • image descriptionSchwann cells that surround large diameter image descriptionaxons (A and B fibers; 2 um or larger) undergo a wrapping process called myelination.
An image showing an axon of a neuron Myelinated by Schwann Cells
An image showing an axon of a neuron Myelinated by Schwann Cells, the schwann cell is labeled
An image showing an axon of a neuron Myelinated by Schwann Cells, the axon and schwann cells are labeled
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  • The process begins when one part of the Schwann cell begins to move along the surface of the axon.
  • As it moves, this leading edge image descriptionslides underneath the outer portion of the Schwann cell, pushing it out of the way.
  • During this repeated wrapping, more and more cytoplasm is pushed to the periphery of the Schwann cell.
  • When the myelinatiion process is image descriptioncomplete, the Schwann cell covers the axon with many layers of plasma membranes, consisting mostly of lipids.
An image showing an axon of a neuron Myelinated by Schwann Cells, the axon and schwann cells are labeled
An image showing an axon of a neuron Myelinated by Schwann Cells after the Myelination process , the axon and schwann cells are labeled
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  • This covering is called a image descriptionmyelin sheath, and the axon is said to be myelinated. The Schwann cell cytoplasm outside the myelin sheath contains the cell image descriptionnucleus and is referred to as the image descriptionneurilemma.
An image showing an axon of a neuron Myelinated by Schwann Cells after the Myelination process , the axon and schwann cells are labeled
An image showing Myelin sheath of schwann cell in addition to an axon of a neuron Myelinated by Schwann Cells, the Myelin sheath , axon and schwann cells are labeled
An image showing Nucleus of the schwann cell in addition to an axon of a neuron Myelinated by Schwann Cells, the Nucleus, Myelin sheath, axon and schwann cells are labeled
An image showing Neurilemma of the schwann cell in addition to an axon of a neuron Myelinated by Schwann Cells, the Neurilemma, Nucleus, Myelin sheath, axon and schwann cells are labeled
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  • Schwann cells are only 0.3 mm to 1.5 mm in length, thus many are required to myelinate the length of a single axon.

Related images:

An image showing the electronmicrographs of a myelinated axon, the myeline is magnified on the left
An image showing the Oligodendrocyte structure, the nucleus, Myeline sheath and the myelinated axon (by the Oligodendrocyte) are labeled
An image showing light micrograph of myelinated neurons at high magnification
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Overview:

An image showing Myelination of axon by the schwann cell, Nucleus, Myelin sheath, and Neurilemma of shwann cell all numbered without answers
An image showing Myelination of axon by the schwann cell, Nucleus, Myelin sheath, and Neurilemma of shwann cell all numbered with answers below
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