| Objective:Nerve fibers distribution, cells size and cells density in the transversal and longitudinal sections of normal rats'sciatic nerve have been experimented. We analyzed nerve morphological distribution in different section as the evidence for the cutting rate of the nerve. In addition, nerve regeneration and nerve fibers distribution in the nerve connection were observed by the different diameter small gap bridging in order to provide the theory and experiment for nerve regeneration and functional reserve after peripheral nerve injury.Method:From up to down along the back, the left thigh and the right thigh the skin and the muscle were cut and the sciatic nerves exposed in 30 adult rats, totally 60 sciatic nerves. The serial sections on rat sciatic nerve were presented by Leica-3000 machine. After dehydration, transparent and HE staining, photographed by Olympus microscope. Stomach artery as the bridging in the same species but different of additional 36 male Wistar rats, separated from the near branch, removed the near nervus peroneus communis 1 cm and kept tibial nerve. The near broken end was turned over and sewed the closed muscle tissue. The 3mm gap was remained between the broken ends of nerve. The kept near nerve and far normal diameter sciatic nerve were sewed together by 10-0 microthread small gap bridging to make the nerve regeneration chamber in order that the morphological nerve regeneration after 7d,14d,21d, 28d,42d,8w,16w.Results:①The nerves cross-section's overall shape was the oval from the proximal to the distal, the right diameter was larger than the left, and nerve distribution was uniform. Nerve trunk near the middle began to branch. Cross-section filled with Schwann cells, the average size of which was 6.25μm×4.75μm, and cell density was 23.15 num/mm2.②The regenerated nerve artery consisted of 5-6 layers of elastic fibers in the full length without curve and narrow. The regenerate chamber was filled with exosmic blood plasma, tissue fluid, amount of nucleolus, but not continuous regenerate nerve fiber after 7 days by the small gap bridging. After 14 days homogeneity in the small gap decreased, but in regenerate chamber there has still been too many cells. There were a few uncontinuous nerve fibers not to reach the section of far nerve. In the elastic fibers connection the small blood tube had the obvious hyperplasia, meanwhile, nerve fibers didn't rush out of the chamber. After 21 days nerve fibers went through lumen continuously and most straightly, only a light curve near the connection. The cells were less than that in 14 days. After 28 days the connection was perfect, the far nerve were thicker, but still thinner than the near. The number and density of the far nerve fibers were more than the near. The bridging blood vessel had no sink and surrounded out of nerve. After 42 days the regenerated nerve fibers turned to be thicker, most of which arranged straightly with the vein hyperplasia inside nerve fibers and bridging tube. After 8 weeks, the near thin nerve regenerated many young axons connected with the far several nerves to be alive. After 16 weeks, diameter of the far nerve fibers was similar to the near, and the quantity of the far was more than the near. The regenerated fiber cells increased and the structure of the bridging tube was entire.Conclusion:①The accurate data was presented for the cut rate of nerve by the research for the normal sciatic nerve distribution, cell size and density.②The normal near sciatic nerve was the structure for nerve functional reserve because it arranged crossly, thickly and tensely.③The study on the morphological sciatic nerve small gap bridging in different time regeneration showed the thin nerve regenerated many axon and connected perfectly in the connection to finish the nerve regeneration.
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