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Module 10: Figure inner ear

Structural organization of the inner ear.

The vestibule has the semicircular canals that function in movement detection. Flow of fluid in the canals excites vestibular and saccular hair cells. Detection of airborne sounds is carried out by the cochlea, which has three fluid-filled compartments: the scala vestibuli, scala media and scala tympani. The stapes, which is one of the small bony ossicles, vibrates the oval window to set up a wave that travels down the length of the scala vestibuli (yellow arrows) and back through the scala tympani, where pressure is adjusted by vibration of the round window. This travelling wave sets up a vibration in the basilar membrane. The latter supports the organ of Corti, which contains the inner and outer hair cells. The stereocilia that project from the apical surface of the hair cells interact with the tectorial membrane, which is made up of a collagenous gel. The endolymph is rich in K+, which is secreted into the scala media by the stria vascularis.