Round window

The Fenestra cochleae (Latin, literally " window of the screw " ) or the round window ( fenestra rotunda ) is a part of the ear of terrestrial vertebrates. It connects the scala tympani ( scala tympani ) of the inner ear with the middle ear.

The cochlea forms, together with the vestibular system, a substantially with liquids ( peri-and endolymph ) filled cavity, which is almost completely embedded in bone. Sound waves are transmitted through the oval window in this system. As there are hardly any liquids and compress the system due to the bony embedding can not expand, is a second opening, the round window, to equalize the pressure.

In detail: The sound waves hit the eardrum, this transfers the vibration to the ossicles in the middle ear; as the last member of the footplate of the stapes and the fenestra vestibuli is associated ( oval window) moves. Thus, the perilymph in the scala vestibuli ( scala vestibuli ) is now vibrated. This is about the helicotrema with the scala tympani in conjunction, so that the fluid moves in opposite directions to do so. The Fenestra cochleae used for pressure compensation.