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Anatomy
Published in Stanley A. Gelfand, Hearing, 2017
Upon exiting the habenula perforata into the organ of Corti, the now unmyelinated neural fibers follow different routes to distribute themselves asymmetrically between the inner and outer hair cells, as shown schematically in Figures 2.33 and 2.34. About 95% of these fibers are inner radial fibers, which course directly out to innervate the inner hair cells. The remaining 5% consist of 2500–3000 outer spiral fibers that cross the tunnel of Corti as basal fibers, and then turn to follow a route of about 0.6 mm toward the base as the outer spiral bundle. These outer spiral fibers then make their way up between the Deiters’ cells to synapse with the outer hair cells.
Anatomy of the Cochlea and Vestibular System: Relating Ultrastructure to Function
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Several different morphologically recognizable types of supporting cell are present in the mature organ of Corti (Figure 47.3b,c). The Deiters’ cells that intercalate between OHCs have cell bodies that contact with each other at their basal end and rest on the BM (Figures 47.4b,d,e and 47.7h). Each one forms a cup-shaped enclosure around the very base of an OHC and its nerve endings (Figure 47.7h, i). Deiters’ cells extend a thin phalangeal process up through the space of Nuel (Figure 47.7h) so that the entire lateral membrane of each OHC is free from contact with another cell (Figures 47.4b and 47.7e). Contact between the OHC and its surrounding supporting cells is only at the apical junctional complex (Figure 47.7e,j) and at the basal cup around the base of hair cell (Figures 47.4b and 47.7e,h,i). The OHCs and IHCs are separated in the radial plane by the outer and inner pillar cells (Figure 47.4b) ‘phalangeal cells’ that are similar in general morphology to the Deiters’ cells, the phalangeal processes of which form the tunnel of Corti, the outer pillar cell buttressing against the underside of the head of the inner pillar cell (Figures 47.4b and 47.7l).123 Unlike OHCs, IHCs are closely surrounded by columnar supporting cells, the inner border cells to the medial side and the phalangeal cells to the lateral side, between the body of the IHC and the inner side of the inner pillar cell (Figures 47.4b,c and 47.7a). Lateral to the outermost (third) row of Deiters’ cells are Hensen’s cells (Figure 47.4b,c and 47.7o) which, in some species contain large lipid droplets that are thought, among other things, to provide additional mass. Additional epithelial cell types including the relatively unspecialized and uncharacterized Claudius cells that form the outer skirt of the organ of Corti ridge (Figure 47.4b,c and 47.7o), and lateral to these are the cuboidal epithelial cells of the outer sulcus that extend to the tissues on the lateral wall of the cochlea. In the basal cochlear coils, sitting on the basilar membrane and covered by the Claudius cells are a group of Boettcher cells (Figure 47.4c and 47.7p) that have a densely staining cytoplasm and multiple infoldings at their cell–cell interfaces. In most species these cells are absent from the apical coils. The function of these cells is still ill-defined but their morphology suggests some role in maintaining the physiological environment in the cochlea. There is also a suggestion they have a role in the maintenance of the BM.124
The applications of targeted delivery for gene therapies in hearing loss
Published in Journal of Drug Targeting, 2023
Melissa Jones, Bozica Kovacevic, Corina Mihaela Ionescu, Susbin Raj Wagle, Christina Quintas, Elaine Y. M. Wong, Momir Mikov, Armin Mooranian, Hani Al-Salami
More specifically, several cell types make up the supporting cells of the organ of Corti, including Deiters cells, pillar cells, Hensen’s cells, Claudius cells, and the cells termed inner supporting cells which primarily consist of phalangeal cells. The organ of Corti’s precise structure has the aforementioned one row of inner and three rows of outer hair cells on one side of the cochlea duct each, with Deiters cells supporting the outer hair cells, whilst the inner hair cells are supported by inner supporting cells; termed inner phalangeal cells and border cells [41,42]. The cells of the organ of Corti, including both sensory and supporting, can be visualised in a representative diagram in Figure 1. The various types of supporting cells possess their own functionalities, dependent upon cell type. Furthermore, supporting cells also have roles in the maintenance and function of sensory cells, in addition to their critical roles in sensory cell development [43].
Direct cellular reprogramming and inner ear regeneration
Published in Expert Opinion on Biological Therapy, 2019
Patrick J. Atkinson, Grace S. Kim, Alan G. Cheng
The mammalian cochlear sensory epithelium consists of an orderly arrangement of hair cells and surrounding supporting cells. Hair cells consist of one row of inner hair cells, the primary sound transducers, and three rows of outer hair cells, which act as amplifiers of low-level sounds [13]. The inner and outer hair cells are separated by the inner and outer pillar cells, supporting cell subtypes that together form the tunnel of Corti (Figure 1). Other subtypes of supporting cells include the Deiters’ cells and inner phalangeal cells that underlie and surround the outer hair cells and the inner hair cells, respectively. As transducers of the cochlea, sensory hair cells are sensitive to a wide variety of insults. After severe damage and extensive hair cell loss, dramatic remodeling of the sensory epithelium can occur [14,15]. For example, after aminoglycoside-induced hair cell loss, supporting cells expand to form a scar-like, flattened epithelium composed of non-specialized cells [15]. The dramatic change in the milieu and architecture of the cochlear sensory epithelium after damage may in part limit its ability to regenerate hair cells, a topic that will be discussed in the following section.
Human cochlear microanatomy – an electron microscopy and super-resolution structured illumination study and review
Published in Hearing, Balance and Communication, 2020
Wei Liu, Rudolf Glueckert, Annelies Schrott-Fischer, Helge Rask-Andersen
Contractile mechanisms along microtubule bundles seem to be of importance for active vibratory responses during hearing, in animals as well as in humans. Inner and OHCs stereocilia and cuticular plates contain contractile elements such as actin together with an intricate cross-linking molecular machinery whose organization is still poorly understood [9]. Actin filaments and microtubules can crosslink in OHCs [10,11]. Contractile proteins were described in supporting cells in guinea pigs by Flock et al. [12] and were noted to be giving stability to the cells. They contain non-muscle β- and γ actin isoforms and α-actinin [13,14] whereas the cuticular plate contains actin, α-actinin, myosin, tropomyosin, spectrin, profilin and fodrin [10,15]. Non-muscle actin subunits are present in human Deiters cells, IPCs and OPCs and contain a remarkable three-dimensional (3D) interacting skeletal system of actin strands and microtubules anchored to the plasma cell membranes (Figure 3). Opposing pillars appear to be coupled with functional elements to relay basilar membrane (BM) vibrations to the reticular lamina (RL) and sensory hair cells that have no direct contact with the BM (Figure 4). In humans, TEM shows a dense meshwork associated with cell junctional complexes at the plasma membrane referred to as surfoskelosomes [13]. These are located in the pillar heads and foot (basal bodies) that contain organized actin and are closely associated with microtubules [16]. Deiters’ cells also express organized actin in basal bodies. Border and phalangeal cells around the IHCs do not express cytoplasmic actin possibly since they are positioned on a rigid fundament operative as principal sensory receptors.