| Myelin incisure | |
|---|---|
 Diagram of longitudinal sections of medullatednerve fibers. (Incisure labeled at upper left.) | |
| Details | |
| System | Nervous system |
| Identifiers | |
| TH | H2.00.06.2.03015 |
| Anatomical terms of microanatomy | |
Myelin incisures (also known asSchmidt-Lanterman clefts,Schmidt-Lanterman incisures,clefts of Schmidt-Lanterman,segments of Lanterman,medullary segments) are small pockets ofcytoplasm left behind during theSchwann cell process ofmyelination.
They arehistological evidence of the small amount of cytoplasm that remains in the inner layer of themyelin sheath created bySchwann cells wrapping tightly around anaxon (nerve fiber).
In theperipheral nervous system (PNS)axons can be either myelinated or unmyelinated. Myelination refers to the insulation of an axon with concentric surrounding layers oflipid membrane (myelin) produced bySchwann cells. These layers are generally uniform and continuous, but due to imperfect nature of the process by whichSchwann cells wrap the nerve axon, this wrapping process can sometimes leave behind small pockets of residualcytoplasm displaced to the periphery during the formation of the myelin sheath. These pockets, or "incisures", can subdivide the myelinated axon into irregular portions. 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 appearab initio in myelination and always extend across the whole radial thickness of the myelin sheath but initially around only part of its circumference. Secondary incisures appear later, in regions of a compact myelin sheath, initially traversing only part of its radial thickness but commonly occupying its whole circumference.[1]
This article incorporates text in thepublic domain frompage 727 of the 20th edition ofGray's Anatomy(1918)
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