Visual Anatomy 視覚解剖学

鼓膜　（こまく、英：tympanic membrane ）

　In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. 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 cochlear fluid. The malleus bone bridges the gap between the eardrum and the other ossicles.
　Rupture or perforation of the eardrum can lead to conductive hearing loss. Collapse or retraction of the eardrum can cause conductive hearing loss or cholesteatoma.

【語句】

・tetrapods：　・membrane：膜　・external ear：外耳　・middle ear：中耳　・ossicles：小骨　・oval window：卵円窓　・cochlea：蝸牛　・ultimately：最後に、結局　・convert：変換する　・amplify：増幅する　・malleus：ツチ骨　・rupture：破裂　・conductive hearing loss：伝導性難聴　・retraction：引っ込めること　・cholesteatoma：真珠腫　

Orientation and relations
　The tympanic membrane is oriented obliquely in the anteroposterior, mediolateral, and superoinferior planes. Consequently, its superoposterior end lies lateral to its anteroinferior end.
　Anatomically, it relates superiorly to the middle cranial fossa, posteriorly to the ossicles and facial nerve, inferiorly to the parotid gland, and anteriorly to the temporomandibular joint
【Regions】
　The eardrum is divided into two general regions: the pars flaccida and the pars tensa. The relatively fragile pars flaccida lies above the lateral process of the malleus between the notch of Rivinus and the anterior and posterior malleal folds. Consisting of two layers and appearing slightly pinkish in hue, it is associated with Eustachian tube dysfunction and cholesteatomas.
　The larger pars tensa consists of three layers: skin, fibrous tissue, and mucosa. Its thick periphery forms a fibrocartilaginous ring called the annulus tympanicus or Gerlach's ligament. while the central umbo tents inward at the level of the tip of malleus. The middle fibrous layer, containing radial, circular, and parabolic fibers, encloses the handle of malleus. Though comparatively robust, the pars tensa is the region more commonly associated with perforations.

【語句】

・consequently：従って　・middle cranial fossa：中頭蓋窩　・parotid gland：耳下腺　・temporomandibular joint：顎関節　・pars flaccida：弛緩部　・pars tensa：緊張部　・fragile：もろい　・lateal process of the malleus：ツチ骨の外側突起　・notch of Rivinus：リビウス切痕　・anterior and posterior malleal folds：前・後ツチ骨ヒダ　・pinkish：ピンクがかった　・hue：色合い　　・Eustachian tube dysfunction：耳管機能障害　・cholesteatomas：真珠腫中耳炎　・mucosa：粘膜　・periphery：周囲、表面　・annulus tympanicus：鼓膜輪　・umbo：鼓膜臍　・parabolic：放物線状の　・handle of malleus：ツチ骨柄　・robust：強固な

【Umbo】
　The manubrium (Latin: handle) of the malleus is firmly attached to the medial surface of the membrane as far as its center, drawing it toward the tympanic cavity. The lateral surface of the membrane is thus concave. The most depressed aspect of this concavity is termed the umbo.
【Nerve supply】
　Sensation of the outer surface of the tympanic membrane is supplied mainly by the auriculotemporal nerve, a branch of the mandibular nerve (cranial nerve V3), with contributions from the auricular branch of the vagus nerve (cranial nerve X), the facial nerve (cranial nerve VII), and possibly the glossopharyngeal nerve (cranial nerve IX). The inner surface of the tympanic membrane is innervated by the glossopharyngeal nerve.

【語句】

・tympanic cavity：鼓室　・concave：凹状の　・concavity：陥没部　・sensation：知覚　・auriculotemporal nerve：耳介側頭神経　・mandibular nerve：下顎神経　・vagus nerve：迷走神経　・glossopharygeal nerve：舌咽神経　

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