Fig. 6. Diagrammatic representation of the movements of the stapes and operculum of the bullfrog at low frequencies. The operculum is portrayed as semitransparent to reveal the flange of the pars interna underneath. In this example, when the pars media is pushed down, which happens when the tympanic membrane is inflected, the footplate is moved out of the oval window. As a result of the coupling between the footplate and operculum, the operculum also moves outwards. Note that the stapes is hinged ventrolaterally but the operculum is hinged dorsomedially.