Electron microscopic structure of the human round window membrane.

The fine structure of the human round window membrane has been investigated. It was found to consist of three layers: the tympanic cavity layer, the middle connective tissue layer, and the scala tympani layer. The middle connective tissue layer is considered the most important part of the round window membrane as it permits the movements of the inner ear fluid caused by the movements of the stapedial foot plate. The strength and elasticity of the membrane is guaranteed by three-dimensionally arranged collagen and elastic fibres and elastic networks in the middle connective tissue layer. The rupture of the round window membrane seems to be due to the diminished number and elasticity of the elastic elements in the middle connective tissue layer of the round window membrane.