The human inner ear consists of the cochlea and the vestibular organ. The base of the cochlea borders the middle ear with the ossicles. The stirrup touches the oval window (fenestra vestibule), the vestibular scale is behind it. It is connected at the end of the cochlea, the apex, to the helicotrema with the tympanic duct. Latter borders the round window that can swing freely. Pressure on the oval window via swinging of the ossicles can be equalized through stretching the round window. The cochlear duct is separated by Reissner’s membrane from the vestibular duct and by the basilar membrane from the tympanic duct. The vestibular and tympanic ducts are filled with perilymph that is exchanged via the helicotrema.