Cochlea

The cochlea is a spiral-shaped, fluid-filled structure in the inner ear that converts sound vibrations into electrical signals carried by the auditory nerve.

Basilar membrane: A flexible partition in the cochlea that vibrates differently along its length in response to sound. Its position-dependent motion separates sound frequencies into distinct locations.
Scala vestibuli: The upper fluid-filled chamber of the cochlea, extending from the oval window toward the apex. It carries pressure waves entering the cochlea through the oval window.
Cochlear implant: An implanted device that electrically stimulates the auditory nerve to provide a sense of sound. It bypasses damaged cochlear hair cells and stimulates auditory pathways directly.
Vestibular system: The inner-ear system that senses head motion and orientation to support balance. It shares the inner ear with the cochlea but primarily serves balance rather than hearing.
Organ of Corti: The sensory structure on the basilar membrane containing hair cells and supporting cells. It houses the cells that turn basilar-membrane motion into neural signals.
Scala media: The cochlear chamber containing endolymph and the organ of Corti. Its specialized fluid and sensory tissue form the cochlea’s central compartment.
Sensorineural hearing loss: Hearing impairment caused by damage to the inner ear or auditory nerve. Damage to cochlear hair cells is a common cause of this form of hearing loss.
Semicircular canals: Three fluid-filled inner-ear loops that detect rotational head movements. Unlike the cochlea’s sound analysis, these canals signal angular head motion.
Hair cell: A sensory cell that converts mechanical deflection of its stereocilia into changes in electrical activity. Cochlear hair cells transduce vibration into signals that can activate auditory neurons.
Scala tympani: The lower fluid-filled chamber of the cochlea, extending from the apex to the round window. It completes the fluid pathway that relieves pressure generated by incoming sound.

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