title: Dissection of the Auditory Bulla in Postnatal Mice: Isolation of the Middle Ear Bones and Histological Analysis.
abstract: In most mammals, auditory ossicles in the middle ear, including the malleus, incus and stapes, are the smallest bones. In mice, a bony structure called the auditory bulla houses the ossicles, whereas the auditory capsule encloses the inner ear, namely the cochlea and semicircular canals. Murine ossicles are essential for hearing and thus of great interest to researchers in the field of otolaryngology, but their metabolism, development, and evolution are highly relevant to other fields. Altered bone metabolism can affect hearing function in adult mice, and various gene-deficient mice show changes in morphogenesis of auditory ossicles in utero. Although murine auditory ossicles are tiny, their manipulation is feasible if one understands their anatomical orientation and 3D structure. Here, we describe how to dissect the auditory bulla and capsule of postnatal mice and then isolate individual ossicles by removing part of the bulla. We also discuss how to embed the bulla and capsule in different orientations to generate paraffin or frozen sections suitable for preparation of longitudinal, horizontal, or frontal sections of the malleus. Finally, we enumerate anatomical differences between mouse and human auditory ossicles. These methods would be useful in analyzing pathological, developmental and evolutionary aspects of auditory ossicles and the middle ear in mice.
authors.affiliation: Laboratory of Cell and Tissue Biology, Keio University School of Medicine.
authors.forename: Ayako
authors.initials: A
authors.lastname: Sakamoto
authors.affiliation: Laboratory of Cell and Tissue Biology, Keio University School of Medicine.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kuroda
authors.affiliation: Department of Otolaryngology Head and Neck Surgery, Keio University School of Medicine.
authors.forename: Sho
authors.initials: S
authors.lastname: Kanzaki
authors.affiliation: Laboratory of Cell and Tissue Biology, Keio University School of Medicine; kmatsuo@keio.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Matsuo
mesh_terms: D000818:Animals; D004429:Ear Ossicles / Q000000981:diagnostic imaging / Q000473:pathology*; D007188:Incus / Q000473:pathology; D008307:Malleus / Q000473:pathology; D051379:Mice; D013199:Stapes / Q000473:pathology; D055114:X-Ray Microtomography