JACOPIN / SCIENCE PHOTO LIBRARY JACOPIN / SCIENCE PHOTO LIBRARY
HEARING, DRAWING Anatomy of the ear and zoom on the organ of audition. Anatomy of the ear : - external ear (with the external auditory meatus by which penetrate the sounds), - middle ear (tympan in clear violet ; ossicles in pinkish beige : malleus, incus and stape ; eustachian tube in dark violet), - internal ear (bony labyrinth in violet, membranous labyrinth in beige), constituted of the semi-circular canals, the vestibule and the cochlea, - Auditory nerve (in yellow). Zoom on the organ of audition (cut-away view accross a winding of the cochlea). The cochlea is divided into three cavities : Scala vestibuli and tympanic canal (on each side), cochlear canal (in pink). The latter is separated from the tympanic canal by a wall, the basilar lamina, that holds the Corti's organ (organ of audition). The scala vestibuli and tympanic canal are filled with perilymph. During the transmission of sound, the vibrations of the stape in the window of the vestibule generate ondulations of the perilymph contained in the rampes (blue arrows), that propagate to the cochlear canal. This makes vibrating the basilar lamina and as a consequence the stereocilia of Corti's organ (in orange). Those vibrations are then converted into nerve impulse, transmitted by the cochlear nerve (in yellow) to the auditory area of the brain. See.
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