The Ultrastructure of the Spiral Ligament in the Rhesus Monkey

Abstract

Electron microscopy of the spiral ligament of the Rhesus monkey reveals two types of fibrocytes. Type I contains a relatively small number of cell organel-les and is found in the deeper part of the spiral ligament and adjacent to the stria vascularis. Type II shows many cell organelles and is located near the surfaces of both scalae vestibuli and tympani, behind the spiral prominence epithelium and external sulcus cells. Fibrocytes establish numerous attachments (fascia occludens, fascia adherens, and macula adherens) with each other and even between the cell processes of the same cell. Type II fibrocytes appear to be actively engaged in fluid metabolism, and often contain long mitochondria with longitudinally arranged cristae. Connective tissue channels are observed between the external sulcus cells extending to the cells of Claudius. The physiological importance of the external sulcus cells is considered and discussed.