Basilar membrane

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Overview of the bony and membranous structures of the labyrinth.

The basilar membrane is a distensible membrane located within the cochlea of the inner ear. It extends horizontally from the apex of the spiral lamina to the osseus cochlea via the spiral ligament, separating the scala media from the scala tympani. It is wider at the apex than at the base near the vestibular window.

The spiral organ (of Corti), containing hair cells (hearing receptor cells), sits on top of the inner surface of the basilar membrane in the scala media. Incoming sound waves make the basilar membrane vibrate and displace, activating the hair cells in the organ of Corti, in turn triggering electrical signals to be sent to the brain. Sound waves of varying frequencies will displace different parts of the basilar membrane along its length in a gradient-like fashion. Closer to the base of the cochlea, the membrane is narrower and stiffer and so will be displaced by higher frequency sounds. At the apex it is wider and more flaccid, thus will be displaced by lower frequency sound waves.