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Vestibular Respiratory Regulation
Published in Alan D. Miller, Armand L. Bianchi, Beverly P. Bishop, Neural Control of the Respiratory Muscles, 2019
The receptor elements of the vestibular system are called hair cells. These cells are flask-or cylinder-shaped, and are joined to adjacent hair cells and supporting cells by tight junctions. Several rows of “hairs” (stereocilia) and a single kinocilium protrude from the apical surface of hair cells. Mechanically gated channels are located along the sides of stereocilia; thin “spring-like” fibers link the channels with an adjacent stereocilium. The mechanical arrangement is such that bending the stereocilia toward the kinocilium results in the opening of channels. The cilia are bathed in endolymph, which has a much more positive potential than the inside of the hair cell. Thus, the opening of channels results in the flow of positive current into the hair cell body.
Physiology of Equilibrium
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
Floris L. Wuyts, Leen K. Maes, An Boudewyns
The kinocilium is located at the tall edge of the bundle. The kinocilium is a true cilium consisting of an axoneme (nine paired microtubules and sometimes an additional central pair of microtubules). The role of the kinocilium is the transmission of stimulus forces to the stereocilia, but this appears not to be essential for mechanotransduction.
The Vestibular System: An Overview of Structure and Function
Published in Kenneth J Ottenbacher, Margaret A Short Degraft, Vestibular Processing Dysfunction in Children, 2013
another canal in the opposite ear. The membranous semicircular canals consist of an endolymph-filled duct and ampulla. The duct is curved and forms the "semicircle". It opens at one end into the utricle and the other end joins with its ampulla. The ampulla contains the neuroepithelium: the crista ampullaris. The crista ampullaris, is in many ways, similar to the macula of the otolith organ. The structure of both the otolith and semicircular canal neuroepithelium is basically the same. The neuroepithelium consists of sensory hair cells, supportive cells, nerve fibers, nerve endings and superstructural elements such as the cupula and otolithic crystals, which can be considered to function as mechanical transducers to transform angular and linear acceleration into pattern-specific afferent nerve signals. Two types of vestibular sensory hair cells have been identified (Figure 2). The Type II hair cell is phylogenetically more primitive and its cell body takes on a columnar appearance. The peripheral processes of several afferent neurons make direct synaptic contact with the Type II hair cell surface. The Type I hair cell has a light-bulb shape, and a peripheral afferent process forms an expanded envelope, or calyx, that intimately envelops the surface of the hair cell. Efferent fibers also interact with both hair cell types. Efferent fibers terminate directly upon the body of cell Type II, thus forming a synapse peripheral to the hair cell-afferent synapse. Efferent fibers to the Type I cell, however, make contact with the afferent calyx, not the surface of the Type I hair cell. Cilia project from the surface of the cuticular plate of each hair cell. From 60 to 100 stereocilia but only one kinocilium project from the surface of each hair cell. The stereocilia are homogenous in cross-section, are rather stiff and are anchored with small rootlets which penetrate through the cuticle. The kinocilium is longer than the longest stereocilium and is found on one side of the bundle of stereocilia. The asymmetry produced by the location of the kinocilium produces a polarization of each hair cell. In the crista of the horizontal semicircular canal, the kinocilium of each hair cell is located on the utricular side of the ampulla, that is, toward the midline; therefore, the polarity of each hair cell is extended to provide polarity of each crista ampullaris. The polarity is reversed in the vertical canal cristae. In the cristae of the vertical canals, the kinocilia are all located on the distal pole of the hair cells, toward the semicircular canal duct. 4 Electrophysiological experiments on the semicircular canals show the consequence of the anatomical polarity. 5 ·6 In a majority of units sampled, spontaneous activity was found when the cupula was in the resting position (Figure 3). When the cupula was deflected in the direction of the kinocilium, the rate of discharge increased. When deflected in the direction away from the kinocilium, the level of spontaneous activity decreased. The polarization of hair cells of the macula of the utricule and saccule
The influence of the subarcuate artery in the superior semicircular canal dehiscence and its frequency on stillbirths: illustrative cases and systematic review
Published in Acta Oto-Laryngologica, 2018
Gabriela Pereira Bom Braga, Jack H. Noble, Eloisa Maria Mello Santiago Gebrim, Robert F. Labadie, Ricardo Ferreira Bento
The clinical relevance for this is that intracanalicular and intracranial pressure differentials become dependent on one another at the dehiscence and produce abnormal stimulation of kinocilia and sterocilia during angular acceleration leading to symptoms such as autophony, tinnitus, hearing loss, dizziness, vertigo, and pressure-induced nystagmus (Hennenbert sign). Individual symptoms are sufficient to impact quality of life, and when combined, can be severely debilitating [15]. Management paradigms include non-operative and operative measures, which includes trigger avoidance, tinnitus retraining therapy, medical managements and frequent follow-up visits with serial imaging. Patients with severely debilitating symptoms who have not experienced adequate relief with conservative measures are considered surgical candidates, but evidence in support of conservative management of SSCD in children has been gleaned from a multitude of single-institution, retrospective studies. In children with SSCD, auditory symptoms often precede vestibular signs, and hearing loss is frequently reported and an early diagnosis should be strived to preserve inner ear functions [15]. Like Brandolini in 2011, we recommend including a high-resolution temporal bone CT study in any diagnosis algorithm of pediatric cochleo-vestibular signs and symptoms [9].
Ciliated cell observation by SEM on the surface of human incudo-malleolar-joint articular cartilage: are they a new chondrocyte phenotype?
Published in Acta Oto-Laryngologica, 2019
Michela Relucenti, Selenia Miglietta, Edoardo Covelli, Pietro Familiari, Ezio Battaglione, Giuseppe Familiari, Maurizio Barbara
The second question regards the motile cilia observed. The primary chondrocyte cilium, a single-cell surface protrusion with a length of about 1–2 µm, has been well described in the literature [18, 19]. This kind of cilium is mechano-sensitive, responding to ultrasounds by modifying its orientation and length. Chondrocytes with primary cilium were observed in the deep part of the cartilage, not on the articular cartilage surface. To our knowledge, no previous description of chondrocytes with long cilia has been reported in the relative literature, so that the existence of a new chondrocyte phenotype, never detected before, could be hypothesized. Second, it would be important to find out what function this new chondrocyte phenotype may play. Motile cilia and primary cilia consist of an axoneme (9 + 2 and 9 + 0) enveloped by a membrane that differs in composition from the plasma membrane due to the presence of specific receptors and ion channels. These structures give the cilia the ability to act as mechano-transducers, chemoreceptors and, in the case of motile cilia, to transduce second messengers, like Ca2+ and cAMP, and consequently modify beat frequency or form [20]. Among the four different cilia arrangements observed, types B, C and D resemble cilia of the genital and respiratory tracts, so that it is possible to hypothesize a role in sensing the synovial fluid osmolarity regulating the circulation of synovial fluid. Conversely, the type A possesses, as a unique feature, a pyramidal arrangement of the cilia, with extra-long cilia (2 or 3) that stem from the cluster, projecting upwards and ending in an antenna-like formation. On the whole, this structure resembles, to some extent, stereocilia with kinocilium of the vestibular organ, but in this case the diameter of the single cilium is homogeneous, whereas stereocilia are narrower at the base (organ-pipe-like).