Morphology of Schmidt-Lanterman incisures of human shoulder plexus nerves in ontogenesis.

The Schmidt-Lanterman incisures are formed in the phase of "loose" myelin at 15-17 weeks of prenatal development with the formation of nodes of Ranvier. The formation of mature Schmidt-Lanterman incisure is completed in the second foetis period. Schmidt-Lanterman incisures distribution in nerve fibres of young men depends on fibre diameter. In the nerves of elderly people the distribution of the incisures in the internode doesn't depend on a fibre diameter. In the nerves of the elderly men the number of incisures is twice as much as that in the young people. The incisural ultrastructure in human nerve is similar to its structure in other mammals.