title: [Functional model of the middle ear ossicles].
abstract: In students' dissection practice, it is very difficult to teach students the structures and functions of the middle ear ossicles. The middle ear ossicles are too small to explain their structures and functions. Models are useful in explaining these points, but there have been no models that accurately explain the movements of the middle ear ossicles and the functions of the muscles in the middle ear. This time, we have made a model of middle ear ossicles. Our ear ossicles are made of paper-mache with metal in it. The incudomalleolar and incudostapedial articulations are made of rubber. The tensor tympani and the stapedius muscles are made of wire and the two wires can be fixed by cord stoppers. Our model explains clearly the following mechanisms of the middle ear ossicles. 1. The mechanism of sound conduction system. When the sound vibrates the tympanic membrane, malleus and incus rotate together. The long process of the incus pushes the head of the stapes. The sound is amplified by leverage. 2. Attenuation of sound by contractions of tensor tympani and stapedius muscles. When a loud sound is transmitted through the ossicular system, the tensor tympani muscle pulls the malleus inward while the stapedius muscle pulls the stapes outward. These two forces oppose each other and increase rigidity of the ossicular system, thus reducing the ossicular conduction. 3. The mechanism of how paralysis of stapedius muscle, caused by an injury to the facial nerve, results in hyperacusis. 4. This model also suggests a possible reason why the pars lucida of the tympanic membrane exists.
authors: School of Oral Health Science, Faculty of Dentistry, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553, Japan.
authors: Takahiro
authors: T
authors: Satoda
authors: Saiji
authors: S
authors: Shimoe
authors: Seicho
authors: S
authors: Makihira
authors: Mitsuhiro
authors: M
authors: Tamamoto
authors: Atsue
authors: A
authors: Matsumoto
authors: Kumiko
authors: K
authors: Hara
authors: Maki
authors: M
authors: Noso
authors: Yoshie
authors: Y
authors: Niitani
authors: Masaru
authors: M
authors: Sugiyama
authors: Toshinobu
authors: T
authors: Takemoto
authors: Takeshi
authors: T
authors: Murayama
authors: Hideaki
authors: H
authors: Amano
authors: Hiroki
authors: H
authors: Nikawa
mesh_terms: D000715:Anatomy / Q000193:education*; D004429:Ear Ossicles / Q000033:anatomy & histology* / Q000502:physiology*; D004432:Ear, Middle / Q000033:anatomy & histology* / Q000502:physiology*; D004501:Education, Medical / Q000379:methods; D006801:Humans; D008953:Models, Anatomic; D013198:Stapedius / Q000033:anatomy & histology; D013664:Teaching Materials; D013719:Tensor Tympani / Q000033:anatomy & histology