Scala tympani

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Overview of the bony and membranous structures of the labyrinth.

The scala typmani (tympanic duct)  is part of the spiral organ (of corti). The cochlear duct divides the cochlear canal into three compartments: the scala media, the scala vestibuli and the scala tympani.
Of the three canals, the scala tympani is the most inferior canal, located beneath the scala media.

Like the scala vestibuli, the scala tympani is a perilymph containing space. The scala tympani connects with the scala vestibuli apically at a small channel called the helicotrema and ends at the round window. The scala vestibuli and scala tympani are seperated by the cochlear duct which lies in the scala media. 

The function of the scala typmani is to transmit sound waves via the perilymph. Soundwaves enter the ear causing vibration of the tympanic membrane and the ossicles. These vibrations are transferred to the vestibular window (oval window), which causes the perilymph inside the scala tympani and scala vestibuli to move.

The movement of the perilymph causes vibrations in the basilar membrane. The basilar membrane forms the roof of the scala tympani. This vibration in turn activates the sensory hair cells in the spiral organ (of Corti).