File:Schmidt-Lanterman cleft cartoon.jpg

Diagram of a Schmidt-Lanterman cleft in a segment of myelin in longitudinal section

The outer Schwann cell membrane is shown above as a pair of lines making a unit about 75 A across. Two such units with a gap between them are seen below, making the axon-Schwann membrane. Each myelin lamella is composed of two such units in contact. The heavy dense lines are produced where the adjacent lamellae are in contact with one another. The lamellae each traverse the cleft after separating at the heavy dense lines. Within the clefts the units composing the lamellae sometimes separate slightly with a gap < 100 A wide between them. This gap is produced by a splitting of the intraperiod line which bisects each myelin lamella (using lamella to mean the struc- tures from center-to-center of each heavy or "major" dense line of compact myelin). The separations between the lamellae in the cleft are much wider than the intralamellar gaps. At the positions indicated by the letters A, B, and C the appearance of segments of cross-sections of the cleft is shown. In A and C inner and outer mesaxons are shown, respectively. The basement membrane layer (b.m.) is indicated above, but not below.

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Reference

<pubmed>13502426</pubmed>| PMC2224316

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