A 3-Dimensional Model of the Human Round Window Membrane.

Objectives: The round window membrane (RWM) is small in size, making it difficult to clarify its shape and structure. The authors examined a 40x magnified 3-dimensional model of the human RWM to clarify its morphologic aspects and characteristics. Methods: An RWM specimen was obtained from an archival, formalin-fixed, decalcified, left temporal bone of an 84-year old female cadaver. The data obtained by laser scanning microscopy were input into a 3-dimensional printer. After a model of the RWM was created, the following features were examined: striae on the surfaces, curvatures, thickness, and areas. Cross sections of the original specimen were made for histological observations. Results: The contour of this RWM model was approximately elliptic, with a saddle shape. When illuminated from the scala tympani side, the surface facing the fossula exhibited dark anterior and clear posterior portions. A borderline appeared where the 2 portions were bound along the short axis of the ellipse. This borderline was identified as the line of inflection. Collagen fibers were shown to run parallel to the borderline in the posterior portion but were fanned out in the anterior portion. Conclusions: The magnified 3-dimensional model clarified gross anatomy and characteristics of the RWM. It is good teaching material for small tissues, such as the RWM.