Figure 1. Anatomy of the inner ear. A: Schematic view of the inner ear showing the cochlear and vestibular parts and the sensory areas, crista, macula, and organ of Corti (shadowed). B: Whole mount preparation of the cochlea showing the basal turn, the apex, the round window (RW), and the oval window (OW). Note the pigmented stria vascularis through the lateral wall (melanin granules at intermediate cell layers). Scale bar 0.5 mm. C: Low magnification of a midmodiolar section from a mouse cochlea. Note the scala vestibule (SV) limiting by the Reissner's membrane (RS) with the scala media (SM) where the auditory receptor is located (red boxes), the scala tympani (ST) with the basilar membrane (BM), and the spiral ganglion (SG, in the osseous Rosenthal's canal). The lateral wall (LW) is directly in contact with the osseous otic capsule. Scale bar 0.5 mm. D: The organ of Corti containing the neurosensorial cells (inner hair cell, IHC; outer hair cells, OHC), the nonsensorial cells (DC: Deiter cells; HC: Hensen cells; CC: Claudius cells; PC: pillar cells), the tectorial membrane (TM), the spiral limbus (SL), the basilar membrane (BM), the tunnel of Corti (asterisk), and the myelinated cochlear nerves fibers (CNF). Scale bar 50 μm (E and F) Synaptophysin (Syn, in E) labeling of presynapses in the IHC and efferent fibers arriving at the IHC and OHC, Neurofilament 200 kD (NF, in F) labeling of the afferent fibers of the organ of Corti and the synapse region. Scale bar 50 μm. (G) Phalloidin histochemistry of the organ of Corti, labeling F-actin in viable sensory epithelium (stereocilia and cuticular plate of hair cells, reticular lamina, and pillar cells). Scale bar 50 μm. H: Semithin section showing the cytoarchitecture of the spiral ganglion (SG). The inset shows electron microphotograph of the ganglionar cells, surrounded by the Schwann cells (SC). The most abundant neurons in the SG, the type I cells, present a myelin sheath, with external compact myelin (CM) and internal loose myelin (LM). Scale bar 5–0.1 μm (inset) and 30 μm. (I) Detail of the mouse lateral wall showing the stria vascularis with the marginal cells (MC) close to the scala media, the intermediate cells (IC), and the basal cells (BC). The spiral ligament (SpL) is the most lateral part that is close to the otic capsule of the cochlea. Scale bar 50 μm. J: Kir4.1 (KCNJ10, an inwardly rectifying K+ channel) expression in the stria vascularis of an aging mouse. Note the relative loss of expression in some patches in the stria (asterisks). This channel is related with the production of the endocochlear potential, thus with an important role in auditory physiology. Scale bar 50 μm. K: Na+-K+-ATPase expression in the stria vascularis, another functional marker of striatal healthiness that are related with ion homeostasis and auditory physiology (Patuzzi, 2011). Scale bar 50 μm. L and M: The sensory epithelium of the vestibular inner ear: the macula and the cristae gross anatomy. L: Cytoarchitecture of a semithin section of the macula (L) and cristae ampullaris (M) showing the morphological characteristics of these vestibular receptors. Note the arrangement of the hair cells (HC) with the stereocilia (asterisks), the supporting cells (SC), the basement membrane (arrows), the otoconial membrane (OM) with otolites, and the vestibular nerve fibers (VNF). Scale bar 50 μm. N and O: Detail of the macula (N) and cristae ampullaris (O) showing the myosin VIIa expression (red, labeling sensory hair cells) and neurofilament 200 kD expression (green, labeling macula nerve fibers). Arrows show the afferent calyx of type I hair cells.
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