Nature of the fine fibrils of the basilar membrane in the cochlea.

Fine fibrils in the basilar membranes of mouse and guinea-pig cochleae were examined by transmission electron microscopy. The fibrils were 10 nm in diameter and ran straight without branching. The fibrils appeared as two parallel lines in longitudinal sections, and round or polygonal in cross-sections, displaying tubular structures with a lumen. They were similar in ultrastructural details to the elastin-associated and elastin-independent microfibrils of Low (1962) in the subcutaneous tissue. It is concluded that the fibrils in the basilar membrane are the microfibrils.