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. Author manuscript; available in PMC: 2018 Mar 15.
Published in final edited form as: Dev Biol. 2017 Feb 1;423(2):126–137. doi: 10.1016/j.ydbio.2017.01.020

Figure 1. Anatomical organization of the mouse inner ear and hair cell stereociliary bundles.

Figure 1

(A) Sensory receptor hair cells are distributed between six sensory organs demarcated by blue shading in this diagrammatic representation of the mouse inner ear. Three vestibular organs, the anterior cristae, posterior cristae and horizontal cristae are associated with the semi-circular canals and detect rotational movements. The anterior and posterior cristae can be distinguished in part by the presence of the eminentia cruciatum, a central region consisting of non-sensory epithelia that is devoid of hair cells, and is not found in the horizontal cristae. Two additional vestibular organs, the utricle and saccule, detect gravity and linear acceleration in the horizontal and vertical planes respectively. A single auditory organ called the organ of Corti detects sound and spirals along the length of the cochlea. (B) The stereociliary bundle of an individual hair cell consists of a staircase array of stereocilia arranged with the tallest adjacent to the kinocilium. The stereocilia are embedded within an actin meshwork called the cuticular plate which is located throughout the apical surface of the hair cell with the exception of a small region where the kinocilium is anchored to an underlying basal body. The cuticular plate can be labeled using antibodies against β2-Spectrin (red) and outlines the fonticulus; the anchorage site of the kinocilium which can be used to visualize stereociliary bundle orientation. Flourescently-tagged phalloidin (green) labels filamentous actin in the stereocilia and cuticular plate as well as intercellular junctions (not illustrated). Hair cells of the vestibular sensory epithelia and auditory hair cells of the cochlea differ in the organization and length of stereocilia yet both have a distinct planar polarity that is evident in the morphology of the stereociliary bundle and the position of the fonticulus. The orientation of the vestibular stereociliary bundle is indicated by the large black arrow.