Inner Ear

The inner ear is the deepest part of the auditory system, located within the temporal bone of the skull. It contains two main structures: the cochlea, responsible for hearing, and the vestibular labyrinth, responsible for balance and spatial orientation. The cochlea is a fluid-filled, spiral-shaped chamber lined with thousands of tiny sensory cells called hair cells. When sound causes the cochlear fluid to move, the hair cells convert mechanical vibrations into electrical signals that travel along the auditory nerve to the brain.

The vestibular system includes three semicircular canals and two otolith organs (the utricle and saccule), which detect head rotation and linear acceleration. Damage to the inner ear is the most common cause of permanent hearing loss. Unlike most tissues in the body, cochlear hair cells in humans do not regenerate once damaged. Causes of inner ear damage include noise exposure, aging, ototoxic medications, genetic conditions, and viral infections.