抄録
Although studies on the cochlear duct in inner ear are occasionally made by means of light-or electron-microscopy, studies on fibrils of the cochlear duct are few. In this study, the fibrous connective tissues of the cochlear duct were analyzed in regard to morphology, composing substances, and the maturing process of the connective tissues. Periodic Acid Methenamine Silver (PAM) and Ruthenium Red (R. R) stains were used to determine the connective tissues.
The materials were the inner ears of young and mature guinea pigs, human fetuses, and adult humans.
A light microscopic study, using H. E, PAS, and Azan-Mallory stains and PAM stain, revealed that the tectorial membrane, limbus spiralis, basilar membrane, spiral ligament, and stria vascularis consisted of collagenous fibrils containing mucopolysac-charide. Electron microscopic studies were made using double staining with uranium acetate and lead, PAM stain (sliced sections for determining neutral polysaccharide or polysaccharide protein), and R. R stain (block materials for determining mucopolysaccharide) revealed the following: a series of fibrils in the limbus spiralis, basilar membrane, spiral ligament, and stria vascularis were related; silver particles were irregularly deposited on the surface of the fibrils (outer silver gilding); although the fibrils showed a strongly positive reaction to PAM (no periodical stripes were observed) they seemed to be immature, fine collagenous fibrils. On the other hand, although the tectorial membrane fibrils showed a strongly positive reaction to PAM and R. R stains, they were morphologically thinner than those of the basilar membrane, therefore seemingly to be immature fine collagenous tissues. Reissner's membrane, although its fibrous structure was not observed, was revealed to be an incomplete basilar membrane which showed a positive reaction to PAM stain. There were marked differences in the basilar membrane of young and mature guinea pigs, the basilar membrane of young guinea pigs having more fibroblasts than those of mature guinea pigs.
The cochlear duct of human fetuses is formed completely between the 23 rd-29 th week of gestation. The tectorial membrane appears at an early stage, and the basilar membrane and the organ of Corti are formed at a late stage.
It is difficult to compare the cochlear duct with other organs because it is a sensory organ and its anatomical structure is very complex. From these results, it was concluded that the fibrils of the cochlear duct should be regarded as being in a specific, immature stage analogous to fine collagenous fibrils in cartilage and the tympanic membrane.
