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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 ...
The neurilemma is underlain by the myelin sheath (also known as the medullary sheath). In the central nervous system, axons are myelinated by oligodendrocytes, thus lack neurilemma. The myelin sheaths of oligodendrocytes do not have neurilemma because excess cytoplasm is directed centrally toward the oligodendrocyte cell body.
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 ...
White matter is the tissue through which messages pass between different areas of grey matter within the central nervous system. The white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons). This myelin is found in almost all long nerve fibers, and acts as an electrical insulation.
Oligodendrocytes are a type of glial cell, non-neuronal cells in the central nervous system.They arise during development from oligodendrocyte precursor cells (OPCs), [8] which can be identified by their expression of a number of antigens, including the ganglioside GD3, [9] [10] [11] the NG2 chondroitin sulfate proteoglycan, and the platelet-derived growth factor-alpha receptor subunit (PDGF ...
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.
These layers are generally uniform and continuous, but due to imperfect nature of the process by which Schwann cells wrap the nerve axon, this wrapping process can sometimes leave behind small pockets of residual cytoplasm displaced to the periphery during the formation of the myelin sheath. These pockets, or "incisures", can subdivide the ...