The spiral organ (of Corti) is the receptor organ for hearing that produces electrical impulses in response to auditory stimuli. It is located in the scala media of the cochlear canal sitting on top of the basilar membrane. The spiral organ (of Corti) is composed of receptor cells known as the hair cells. It contains three rows of outer hair cells and one row of inner hair cells. The hair cells are so named because they contain hair-like projections on the apical part of their cell membrane, known as stereocilia. The stereocilia are embedded in a gel-like structure called the tectorial membrane. The lower surface of the tectorial membrane harbours a longitudinal ridge called the Hensen’s stripe that anchors the tectorial membrane to the inner and outer border cells. As the perilymph moves in response to sound waves, it shifts the basilar membrane respectively to the tectorial membrane. These shifts between the tectorial and basilar membranes bend the stereocilia, causing the hair cells to depolarize and release the neurotransmitters (glutamate) that transmits the sound information to the cochlear nerve.

Aside from the hair cells, the spiral organ (of Corti) contains a number of supporting cells. From the outer edge to the inner edge of the organ, these are: cuboid external supporting cells (Claudius cells), outer border cells (Hensen’s cells), outer phalangeal cells (Deiters’ cells), pillar cells, inner phalangeal cells and border cells. These supporting cells have distinct morphologies in relation to their functions. The outer and inner phalangeal cells surround and support the basolateral parts of both inner and outer hair cells. Between the outer and inner complexes of hair cells and phalangeal cells, there is a cavity known as the inner tunnel (of Corti). This tunnel is formed by the arching internal and external pillar epithelial cells.

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