A, Representation of the human inner ear A, Representation of the human inner ear. The mammalian ear is composed of three compartments: the outer ear made up of the auricle and external auditory canal; the middle ear made up of the ossicles within the tympanic cavity; and the inner ear which consists of six sensory organs, namely the five vestibular end organs (saccule, utricle, and three semicircular canals) and the cochlea. B, Cross-section through the cochlear duct. The membranous labyrinth of the cochlea (cochlear duct) divides the bony labyrinth into three canals: the scala vestibuli and the scala tympani, both filled with perilymph, and the scala media, filled with endolymph. The organ of Corti, which is the auditory transduction apparatus, protrudes in the scala media. This organ is made up of (a) an array of sensory cells, that is, the single row of inner hair cells (ihc) and three rows of outer hair cells (ohc), and (b) different types of supporting cells (p, d, h). An acellular gel, the tectorial membrane, covers it. The organ of Corti is flanked by the epithelial cells of the inner sulcus (is) on the medial side and by the Claudius' cells (c) on the lateral side. The stria vascularis, on the lateral wall of the cochlear duct, is responsible for the secretion of K+ into the endolymph. Different types of fibrocytes surround the cochlear epithelium. Other abbreviations are: i = interdental cells; p = pillar cells; d = Deiter's cells; h = Hensen's cells; sp = spiral prominence. (Modified from Kalatzis V, Petit C.35 Used with permission.). C, Representation of a sensory inner hair cell. Note the highly organized hair bundle, made of several rows of stereocilia, at the apical pole of the cell. The ribbon synapse has particular structural and functional features. Three specific structures of the actin cytoskeleton are shown, namely (a) the filaments of the stereocilia, (b) the cuticular plate, a dense meshwork of horizontal filaments running parallel to the apical cell surface, and (c) the cortical network, beneath the plasma membrane. Source: Hereditary Hearing Loss, The Online Metabolic and Molecular Bases of Inherited Disease Citation: Valle D, Beaudet AL, Vogelstein B, Kinzler KW, Antonarakis SE, Ballabio A, Gibson K, Mitchell G. The Online Metabolic and Molecular Bases of Inherited Disease; 2014 Available at: https://ommbid.mhmedical.com/DownloadImage.aspx?image=/data/Books/971/ch254fg3.png&sec=62664768&BookID=971&ChapterSecID=62664757&imagename= Accessed: November 01, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved