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The myelin sheath of long nerves was discovered and named by German pathological anatomist Rudolf Virchow [21] in 1854. [22] French pathologist and anatomist Louis-Antoine Ranvier later discovered the nodes, or gaps, in the myelin sheath that now bear his name.
In the PNS, myelin protein zero (MPZ or P0) has a similar role to that of PLP in the CNS in that it is involved in holding together the multiple concentric layers of glial cell membrane that constitute the myelin sheath. The primary lipid of myelin is a glycolipid called galactocerebroside. The intertwining hydrocarbon chains of sphingomyelin ...
A well-developed Schwann cell is shaped like a rolled-up sheet of paper, with layers of myelin between each coil. The inner layers of the wrapping, which are predominantly membrane material, form the myelin sheath, while the outermost layer of nucleated cytoplasm forms the neurilemma. Only a small volume of residual cytoplasm allows ...
These staggered clefts also provide communication channels between layers by connecting the outer collar of cytoplasm of the Schwann cell to the deepest layer of myelin sheath. Primary incisures appear ab initio in myelination and always extend across the whole radial thickness of the myelin sheath but initially around only part of its ...
The myelin sheath is not continuous but is segmented along the axon's length at gaps known as the nodes of Ranvier. In the peripheral nervous system the myelination of axons is carried out by Schwann cells. [1] Oligodendrocytes are found exclusively in the CNS, which comprises the brain and spinal cord.
The myelin sheath insulates the nerve fiber from the extracellular fluid and speeds up signal conduction along the nerve fiber. [34] In the peripheral nervous system, Schwann cells are responsible for myelin production. These cells envelop nerve fibers of the PNS by winding repeatedly around them. This process creates a myelin sheath, which not ...
Cross section of an axon: (1) Axon (2) Nucleus (3) Schwann cell (4) Myelin sheath (5) Neurilemma. In the nervous system, axons may be myelinated, or unmyelinated. This is the provision of an insulating layer, called a myelin sheath. The myelin membrane is unique in its relatively high lipid to protein ratio. [17]
The perineurium is a protective sheath that surrounds a nerve fascicle. [1] This bundles together axons targeting the same anatomical location. [1] The perineurium is composed from fibroblasts. [2] In the peripheral nervous system, the myelin sheath of each axon in a nerve is wrapped in a delicate protective sheath known as the endoneurium.