Ultrastructural Organization of the Epithelial Lining in the Endolymphatic Duct and Sac in the Guinea Pig

Abstract

The finer details of the epithelial lining of the endolymphatic duct and the proximal, intermediate and distal portions of the endolymphatic sac have been described. The most highly differentiated and active part of the entire areas was the intermediate portion where pinocytosis appeared to be a main function. These active cells demonstrated numerous microvilli, pedicels, concentration of mitochondria, many short endoplasmic reticuli and a rich vacuolar system. The infolding of the cytoplasmic membrane was noted near the base of the cell and particularly between adjacent cells. A rich network of the capillaries with fenestrated endothelium was observed in relation to the basement membrane of the sac proper. The epithelial organization and vascularization of this area seemed to be ideally suited for passing fluid from the lumen towards the loose connective tissue.