246 Acta Otorrinolaringol Esp. 2007;58(6):246-51 Introduction and objetives: The columella of birds, often cited in the literature, has yet to be adequately described. We aim to give an account of this transmission element, describing its anchoring systems and detailing the muscle associated to it. Material and method: We performed microscopic dissection and obtained images of ostrich specimens (Struthio camelus), chosen because it is the bird with the largest head. Results: We describe the columella: the osseous tripod formed on its external section (extracolumella), the conic shape of its inner section (stapedial), and links to the tympanic membrane and the oval window. We describe its anchoring system: posterior ligament and annular ligament. We conclude by describing the characteristics of the columella muscle, its insertions and the fibrous vein surrounding it. Conclusions: The avian middle ear is a valid model for understanding the mechanical characteristics of the human ear repaired with total ossicular replacement prosthesis, ie replacement of the ossicular chain by a single element. We highlight an apparent contradiction: the existing muscle is inserted into the columella in an area close to the tympanic membrane rather than adjacent to the oval window. Key words: Middle ear. Columella. Muscle. Struthio camelus. Del oído medio de las aves (Struthio camelus). Datos para la fisiología de la transmisión en sistemas de un único osículo en la cadena Introducción y objetivos: La columela de las aves, citada frecuentemente en la literatura, no aparece descrita conve- nientemente. Pretendemos mostrar este elemento de trans- misión sonora precisando sus sistemas de anclaje y fijación y detallando el músculo de que dispone. Material y método: Realizamos una disección microscópi- ca de especímenes de avestruz (Struthio camelus), y obtuvi- mos y procesamos imágenes de éstos. Escogimos este ani- mal por ser el ave con mayor tamaño cefálico. Resultados: Se describe la columela: el trípode óseo que se forma en su porción externa (extracolumela), la forma cóni- ca de su porción interna (estapedial), sus relaciones con la membrana timpánica y con la ventana oval. Mostramos sus medios de anclaje: ligamento posterior y ligamento anular. Relatamos las características del músculo de la columela, sus inserciones y la potente vaina fibrosa que lo rodea. Conclusiones: El oído medio de las aves es un modelo vá- lido para la comprensión de las características mecánicas del oído humano, en el que se sustituye la cadena osicular por un solo elemento de transmisión sonora. Denotamos una aparente paradoja: el músculo existente se inserta en la columela en un lugar próximo a la membrana timpánica, en vez de en la proximidad de la ventana oval. Palabras clave: Oído medio. Columela. Músculo. Struthio camelus. The authors have not indicated any conflict of interest. Correspondence: Dr. L.A. Vallejo Valdezate. Dr. Sánchez Villares, 17, 1.º B. 47014 Valladolid. España. E-mail: lvallejoval@telefonica.net Received March 5, 2007. Accepted for publication April 10, 2007. INTRODUCTION In amphibians and Sauropsidae (reptiles and birds), communication between the tympanic membrane and the oval window is established due to a single bone or osteocartilaginous element called the columella. The classic treatises distinguish between 2 areas in the columella, the medial area, which is bone (stapedial portion), and the lateral area, which is cartilaginous (extracolumella) 1,2 ; both are found together in an articulation with synchrondosis to form an elastic concatenation to protect against trauma. The insertion area of the columella in the tympanum is always wide, with various forms, plate, fan, arch, etc. 2 In 2002, a dynamic three-dimensional computerized model was published, using the finite element method, 3 which sought to realize a revision of the physiology of the middle ear. Recently the remodelling of the middle ear ■ ORIGINAL ARTICLE The Avian Middle Ear (Struthio camelus). Data for the Physiology of Sound Transmission in Systems With a Single Ossicle in the Chain Luis Ángel Vallejo Valdezate, a Elisa Gil-Carcedo Sañudo, a María Dolores Gil-Carcedo Sañudo, b Manuel Pablos López, b and Luis María Gil-Carcedo García a a Cátedra de ORL y PCF, Universidad de Valladolid, Valladolid, Spain b Facultad de Veterinaria, Universidad de León, León, Spain