Tympanosclerosis. An electron microscopic study of matrix vesicles.

The ultrastructure of tympanosclerotic tissue has been studied and compared with other processes of fibrogenesis and calcification. Evidence is presented of the presence of large numbers of extracellular membrane-bound matrix vesicles and their role as the site of primary calcification in tympanosclerosis. Calcified spherular structures are formed and fuse into larger structures lined by a lamina limitans indicating the lines of arrested calcification in the collagenous matrix.