Cochlea
Sensory (eye & ear)OrgansHeadLeft and right
View left in 3D View right in 3D
- What it is
- The spiral organ of hearing: a bony tube coiled two and a half turns around a central core (the modiolus), like a snail shell, tapering from the wide basal turn to the apex. Inside, three fluid channels run its whole length: scala vestibuli, cochlear duct (scala media) and scala tympani.
- Function
- Converts fluid pressure waves into nerve impulses, high frequencies at the base and low frequencies at the apex (tonotopy).
- Size
- About 9 mm across the base and 5 mm high; uncoiled length 32-35 mm; 2.5-2.75 turns.
- Clinical note
- Its apex points forward and outward; the basal turn bulges into the middle ear as the promontory. Cochlear implants thread an electrode along the scala tympani.