The inner ear of the human ear consists of the cochlea and the vestibular organ. The base of the cochlea is next to the tympanum with the ossicles. The stirrup touches the so-called oval window (fenestra vestibule or fenestra ovalis) that separates it from the Scala vestibuli. Its apex is connected via the helicotrema with the Scala tympani. Latter adjoins with its base the round window which can swing freely. Pressure on the oval window by swinging ossicles can thus be compensated by stretching the oval window. The vestibular membrane separates the Scala media from the Scala vestibule, and the basilar membrane separates it from the Scala tympani. The Scala vestibule and the Scala tympani are filled with perilymph that is exchanged via the helicotrema between both ducts. The Scala media contains endolymph. Both liquids have a fundamentally different composition.
