Electron microscopic study of cat meninges

The intervascular portions of the encephalic dura mater, arachnoid membrane and pia mater were studied with special reference to their spatial relationships. The cell types were analyzed at electron microscopic level. An outer dural layer, composed of typically elongated fibroblasts and large intercellular spaces was identified. The middle dural layer was composed of collagenous connective tissue matrix together with some fibrocytes scattered in it. The inner dural layer showed epithelium-like arranged cells with light cytoplasm and long processes. The electron-dense band, measuring about 20 nm in width, located between dura mater and arachnoid was not so prominent as in the previously investigated experimental animals. The intercellular contacts among the cells of the outer arachnoid layer included maculae and zonulae adherentes and gap junctions mainly, while the tight junctions observed were quite rare. Following the arachnoid trabecular layer, an inner arachnoid layer could be hardly demonstrated. The pial cells were differentiated into 2 distinct layers, bordering the narrow and discontinuous pial space.