Also located within the cochlea are tiny hair cells. They are specifically found within the organ of Corti and are essential for proper hearing. At birth we have about 12,000 hair cells. Hair cells can be damaged and lost throughout our lifetime from loud noises or other conditions, and once they are lost these cells do not regenerate.

The human cochlea contains on the order of 3,500 inner hair cells and 12,000 outer hair cells at birth. The outer hair cells mechanically amplify low-level sound that enters the cochlea. The amplification may be powered by the movement of their hair bundles, or by an electrically driven motility of their cell bodies.

We have two types of hair cells in our cochlea: inner hair cells (we have about 3,500 per ear) and outer hair cells (we have about 12,000 per ear). Inner hair cells collect and relay sound information to the brain through the auditory nerve.

The hair cells are arranged in four rows in the Organ of Corti along the entire length of the cochlear coil. Three rows consist of outer hair cells (OHCs) and one row consists of inner hair cells (IHCs). The inner hair cells provide the main neural output of the cochlea.

Cochlear, as well as vestibular, sensory cells are called hair cells because they are characterised by having a cuticular plate with a tuft of stereocilia bathing in the surrounding endolymph. The cell body itself is localised in the perilymph compartment (see transverse section of the organ of Corti).