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:''Not to be confused with the secondary tympanic membrane of the round window'' In human anatomy, the eardrum, or tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear, and then to the oval window in the fluid-filled cochlea. Hence, it ultimately converts and amplifies vibration in air to vibration in fluid. The malleus bone bridges the gap between the eardrum and the other ossicles.〔Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. The Middle Ear. Available from: http://www.ncbi.nlm.nih.gov/books/NBK11076/〕 Rupture or perforation of the eardrum can lead to conductive hearing loss. Collapse or retraction of the eardrum can also cause conductive hearing loss or even cholesteatoma. ==Structure== There are two general regions of the tympanic membrane: the pars flaccida upper region and the pars tensa. The pars flaccida consists of two layers, is relatively fragile, and is associated with eustachian tube dysfunction and cholesteatomas. The larger pars tensa region consists of three layers: skin, fibrous tissue, and mucosa. It is comparatively robust, and is the region most commonly associated with perforations. The pars tensa forms most of the tympanic membrane. Its periphery is thickened to form a fibrocartilaginous ring called the anulus tympanicus. The central part of the pars tensa is tented inwards at the level of the tip of malleus and is called the umbo. A cone of light can be seen radiating from the tip of the malleus to the periphery in the antero-inferior quadrant. The pars flaccida is situated above the lateral process of the malleus between the notch of Rivinus and the anterior and posterior malleal folds. It appears slightly pinkish. 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「Eardrum」の詳細全文を読む スポンサード リンク
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