Hierarchical levels of the morphological organization of nerve fibers in the human corpus callosum.

Abstract

Background. At present, the idea of the structural content of corpus callosum is extremely simplified. In fact, in the myeloarchitectonics of the corpus callosum, there is a definite form of order between the structures that form it. Objective. The purpose of this study is to elucidate the nature of the corpus callosum structures organization at the microscopic level. Methods. The material used was plates of total sagittal sections of the corpus callosum of people aged 36 to 60 that were preliminarily fixed in 10% neutral formalin solution. After washing and dehydration, some of them were enclosed in paraffin blocks. After that, serial sections, about 10 mm thick, were obtained from those blocks and further they were stained with hematoxylin and eosin using Van Gieson’s method. The remaining mounts of sagittal sections of the corpus callosum were subjected to plastination in epoxy resin. After complete polymerization, polished sections of different thicknesses with the preparations of the corpus callosum in them were obtained from the epoxy plates. Then they were stained with a 1% solution of methylene blue in 1% borax solution. The study of paraffin sections and epoxy sections was carried out with the help of a binocular magnifier МБС-9 and a light microscope Конус equipped with a digital photo adapter. Results. In the corpus callosum a certain number of isolated commissural ropes is integrated. They consist of a dense aggregate of stratified sections - fascicular choruses, which in turn are separated by narrow interstitial spaces in which capillary-type blood microvessels are localized. These interfascicular layers provide lateral spurs dividing fascicular portions into segments - subfascicular portions. Within the subfascicular portions, nodal cells are dispersed, in which interfascicular oligodendrocytes form a dense cellular network. Within their limits the most minimal sets of myelinated nerve fibers called cellular portions are concentrated. Conclusion. The existence of four levels of the structural organization of commissural conductors in the corpus callosum is established. They are in a superordinate order: 1 - commissural cords - subunits of the corpus callosum; 2 - fascicular portions - subunits of commissural ropes; 3 - subfascicular portions - subunits of fascicular choruses; 4 - cellular portions - the most minimal set of myelinated nerve fibers. All these elements are integrated into a single system of commissural tracts by a complex network of interstitial interlayers, the organization of which is subordinated to the character of blood microvessels branching.