> Inner Ear
Drawings: S. Blatrix
The inner ear corresponds to 2 distinct sensory organs: the balance organ or vestibule, and the hearing organ or cochlea, which have a similar embryological origin, the otic vesicle. Both organs also share morphological and physiological properties, such as hair cells and the transduction mechanism.
Vestibule and cochlea: two sensory organs of the inner ear
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Two sensory organs are located in the inner ear. The vestibule is the organ of equilibrium and the cochlea the organ of hearing. They share a common embryonic origin (otic vesicle), plus different morphological or physiological properties such as endolymph, hair cells and mechano-transduction. |
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1. Anterior semicircular canal 2. Ampulla (superior canal) 3. Ampulla (lateral canal) 4. Sacculus 5. Cochlear duct 6. Helicotrema 7. Lateral (horizontal) canal 8. Posterior canal 9. Ampulla (posterior canal) 10. Oval window 11. Round window 12. Vestibular duct (scala vestibuli) 13. Tympanic duct (scala tympani) 14. Utricule |
In situ schematic drawing of the human inner ear
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| The bone has been removed to visualise the vestibule (1), the VIIIth nerve (2) , and the basal portion of the cochlear duct (3), housing the organ of Corti. The rest of the cochlea (4) is covered by the bony capsule. The VIIIth nerve is formed by the vestibular and cochlear nerves which merge before entering the brain. |
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Frequency distribution along the human cochlea basilar membrane: passive tonotopy
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From base (20 kHz) to apex (20 Hz), some characteristic frequencies are indicated. See also an animated cartoon below. |
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Animated cartoon of the cochlear tonotopy |
