Abstract
In regard to the vestibular endolymphatic tube and sac, there is still some obscurity in details and controversial opinions of their morphology and function.
In order to review the fundamental structure, a light and electronmicroscopic study was performed, referring further to general pathological changes noted in 40 consecutive autopsy cases. Histologically, this endolymphatic pathway is divided into three portions: proximal, intermediate and distal. The cells lining the tube and sac are characterized by the abundance of intracytoplasmic fibrils as noted in myoepithelial cells. In the intermediate portion with a rugiform and loose subepithelial fibrous stroma, the light cells with secretory granules are identified besides the chief cells and the wedge-shaped dark cells. From these findings, the hydrodynamic action of endolymph is thought to be controlled by the lining cells with secretory and reabsorptive functions. A valve-like action of rugous structure and the tension of the dura possibly play a role to regulate the flow of endolymph.
In general, pathological changes noted in the aqueduct seem to be limited in variety because of the structural simplicity of this pathway and the surroundings, but it is noteworthy that the primary and secondary disease processes of the patients reflect in some extent to this apparatus with or without functional disorders.
