EARLY MYELINATION OF THE MUSCULOCUTANEOUS AND SUPERFICIAL PERONEAL NERVES

The musculocutaneous and superficial peroneal nerves are studied at 3-4-month fetus in the proximal and distal parts. In the proximal part both nerves consist of the fibers intended for an innervation of muscles and skin. Distal part this nerves consists of the fibers of an innervation which is consists of only skin and it’s derivate. The pieces musculocutaneous and the superficial peroneal nerves were investigated by a light and electron microscopic methods. According to a research, process of myelination of nerve fibers results from the difficult interaction of a neurolemmocyte with an axon. Nerve fibers, the innervating muscles of the upper and lower limb are exposed to more accelerated myelination, than the fibers supplying skin. The myelin sheath can be formed around an axon with a diameter less than 1 mc. At early stages of myelination are noted the hanging orientation of internal and external mesaxons. The size of a cross cut of unmyelination nerve fibers depend on the size of groups where they are located. In process of increase in amount of nerve fibers in group’s diameter of an axon decreases. In a prenatal ontogenesis between thickness of a myelin sheath and diameter of the axon, there is a rectilinear correlative communication. In some cases, divergences from the general regularity are noted. It is characteristic of earlier stages of the process myelination.