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The cochlea (, kōhlias, meaning ''spiral'' or ''snail shell'') is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.5 turns around its axis, the modiolus.〔 〕 A core component of the cochlea is the Organ of Corti, the sensory organ of hearing, which is distributed along the partition separating fluid chambers in the coiled tapered tube of the cochlea. The name is derived from the Latin word for ''snail shell'', which in turn is from the Greek κοχλίας ''kokhlias'' ("snail, screw"), from κόχλος ''kokhlos'' ("spiral shell")〔(etymology of "cochleㄷa" ),〕 in reference to its coiled shape; the cochlea is coiled in mammals with the exception of monotremes. ==Structure== The cochlea (plural is cochleae) is a spiralled, hollow, conical chamber of bone, in which waves propagate from the ''base'' (near the middle ear and the oval window) to the ''apex'' (the top or center of the spiral). Rosenthal's canal or the spiral canal of the cochlea is a section of the bony labyrinth of the inner ear that is approximately 30 mm long and makes 2¾ turns about the modiolus. The cochlear structures include: * Three ''scalae'' or chambers: * * the scala vestibuli (containing perilymph), which lies superior to the cochlear duct and abuts the oval window * * the scala tympani (containing perilymph), which lies inferior to the scala media and terminates at the round window * * the scala media (containing endolymph), or cochlear duct, a region of high potassium ion concentration that the stereocilia of the hair cells project into * The helicotrema, the location where the scala tympani and the scala vestibuli merge, at the apex of the cochlea * Reissner's membrane, which separates the scala vestibuli from the scala media * The basilar membrane, a main structural element that separates the scala media from the scala tympani and determines the mechanical wave propagation properties of the cochlear partition * The Organ of Corti, the sensory epithelium, a cellular layer on the basilar membrane, in which sensory hair cells are powered by the potential difference between the perilymph and the endolymph * hair cells, sensory cells in the Organ of Corti, topped with hair-like structures called stereocilia or stereovilli. The cochlea is a portion of the inner ear that looks like a snail shell (cochlea is Greek for snail.) The cochlea receives sound in the form of vibrations, which cause the stereocilia to move. The stereocilia then convert these vibrations into nerve impulses which are taken up to the brain to be interpreted. Two of the three fluid sections are canals and the third is a sensitive 'organ of Corti' which detects pressure impulses which travel along the auditory nerve to the brain. The two canals are called the vestibular canal and the tympanic canal. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cochlea」の詳細全文を読む スポンサード リンク
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