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inner earOverview

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thumbnail inner ear 4x thumbnail inner ear 10x
thumbnail inner ear 20x thumbnail inner ear 40x

The inner ear consists of the vestibule, the three semicircular canals, and the cochlea. Inside the vestibule and the semicircular canals are the utricle, saccule, and semicircular canals (see Diagram of Inner Ear), which comprise the vestibular system that is involved in balance maintenance. The cochlea (“snail shell”) of the mouse makes one and a half turns around a central bony axis, the modiolus, which houses the spiral ganglion and the cochlear nerve. Inside the cochlea are three compartments: the cochlear duct (scala media), scala vestibuli, and scala tympani. The Reissner’s (vestibular) membrane, containing two layers of simple squamous epithelium, forms the roof of the cochlear duct and the floor of the scala vestibuli. The basilar membrane forms the floor of the cochlear duct and the roof of the scala tympani. The side of the basilar membrane facing the scala tympani is lined with epithelium, whereas the side facing the cochlear duct is occupied by the spiral limbus and the organ of Corti. The cells of the spiral limbus secrete the tectorial membrane. The organ of Corti is the organ of hearing and is composed of supporting cells and sensory cells with many stereocilia, whose tips are covered by the tectorial membrane.

The 4X micrograph is a transversal section of a decalcified head showing the three compartments of the cochlea. The 10X and 20X micrographs display, in increasing detail, the spiral limbus and spiral ganglion. Neurons of the spiral ganglion and fibers of the cochlear nerve are visible in the 40X micrograph.

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