The development of the nervous system is very complex and there are few studies about the organization of the brain envoltories related to the encephalus growing. Using the rat as an animal model, it was proposed to evaluate the several structural aspects of paquimeninge and leptomeninge in different ages. It was used 4 groups of different ages and processed according to the techniques of the light and transmission microscopy. It was verified that the adult rats present a higher area of collagen fibers of type I and III, if compared to the others groups. It was found that, the collagen fibers of type III occupy, in all analyzed groups, a higher area when compared to type I fibers. The results reveal that the Weigert Oxona's staining, which shows elastics, elauninics, and oxitalanics fibers, showed a statistically difference when compared to the Weigert's staining and Verhoeff's staining that show elauninics and elastics fibers, respectively. The ultra-structural aspects demonstrated the presence of many fibroblasts and mitochondria in the paquimeninge and also in the leptomeninges of the neonats and adults groups, indicating the high cellular activity and consequently, an intense formation of conjunctive tissue. As collagen fibers of type III acting on the structural maintenance of delicate and expansive tissues, the study shows that the function of the encephalic meninges are not only related to the to resistance to tractions and tensions that the encephalus is subjected. But also the function related to the distensibility of the meningeos and brain vases according to the sanguineous apport in several specific functions of the nervous system.
Encephalic meninges; collagen; elastic fibers; histomorphometry
