-
Acta Otorrinolaringologica Espanola 2015
Topics: Animals; Humans; Infant, Newborn; Mastoid; Petrous Bone; Semicircular Ducts; Tomography, X-Ray Computed
PubMed: 24342700
DOI: 10.1016/j.otorri.2013.07.008 -
Journal of Anatomy Feb 2016The inner ear of mammals consists of the cochlea, which is involved with the sense of hearing, and the vestibule and three semicircular canals, which are involved with... (Review)
Review
The inner ear of mammals consists of the cochlea, which is involved with the sense of hearing, and the vestibule and three semicircular canals, which are involved with the sense of balance. Although different regions of the inner ear contribute to different functions, the bony chambers and membranous ducts are morphologically continuous. The gross anatomy of the cochlea that has been related to auditory physiologies includes overall size of the structure, including volume and total spiral length, development of internal cochlear structures, including the primary and secondary bony laminae, morphology of the spiral nerve ganglion, and the nature of cochlear coiling, including total number of turns completed by the cochlear canal and the relative diameters of the basal and apical turns. The overall sizes, shapes, and orientations of the semicircular canals are related to sensitivity to head rotations and possibly locomotor behaviors. Intraspecific variation, primarily in the shape and orientation of the semicircular canals, may provide additional clues to help us better understand form and function of the inner ear.
Topics: Animals; Ear, Inner; Hearing; Mammals
PubMed: 25911945
DOI: 10.1111/joa.12308 -
Biological Cybernetics Oct 2020The semicircular ducts (SCDs) of the vestibular system play an instrumental role in equilibration and rotation perception of vertebrates. The present paper is a review... (Review)
Review
The semicircular ducts (SCDs) of the vestibular system play an instrumental role in equilibration and rotation perception of vertebrates. The present paper is a review of quantitative approaches and shows how SCDs function. It consists of three parts. First, the biophysical mechanisms of an SCD system composed of three mutually connected ducts, allowing endolymph to flow from one duct into another one, are analysed. The flow is quantified by solving the continuity equations in conjunction with the equations of motion of the SCD hydrodynamics. This leads to mathematical expressions that are suitable for further analytical and numerical analysis. Second, analytical solutions are derived through four simplifying steps while keeping the essentials of the coupled system intact. Some examples of flow distributions for different rotations are given. Third, the focus is on the transducer function of the SCDs. The complex structure of the mechano-electrical transduction apparatus inside the ampullae is described, and the consequences for sensitivity and frequency response are evaluated. Furthermore, both the contributions of the different terms of the equations of motion and the influence of Brownian motion are analysed. Finally, size limitations, allometry and evolutionary aspects are taken into account.
Topics: Animals; Endolymph; Motion; Semicircular Canals; Semicircular Ducts; Vertebrates
PubMed: 32889629
DOI: 10.1007/s00422-020-00842-w -
PloS One 2022Spider morph ball pythons are a frequently-bred designer morph with striking alterations of the skin color pattern. We created high-resolution μCT-image series through...
Spider morph ball pythons are a frequently-bred designer morph with striking alterations of the skin color pattern. We created high-resolution μCT-image series through the otic region of the skulls, used 3D-reconstruction software for rendering anatomical models, and compared the anatomy of the semicircular ducts, sacculus and ampullae of wildtype Python regius (ball python) with spider morph snakes. All spider morph snakes showed the wobble condition (i.e., twisting movements of the head, impaired locomotion, difficulty striking or constricting prey items). We describe the inner ear structures in wildtype and spider morph snakes and report a deviant morphology of semicircular canals, ampullae and sacculus in the latter. We also report about associated differences in the desmal skull bones of spider morph snakes, which were characterized by wider semicircular canals, ampullae widened and difficult to discern in μCT, a deformed crus communis, and a small sacculus with a highly deviant X-ray morphology as compared to wildtype individuals. We observed considerable intra- and interindividual variability of these features. This deviant morphology in spider morph snakes could easily be associated with an impairment of sense of equilibrium and the observed neurological wobble condition. Limitations in sample size prevent statistical analyses, but the anatomical evidence is strong enough to support an association between the wobble condition and a malformation of the inner ear structures. A link between artificially selected alterations in pattern and specific color design with neural-crest associated developmental malformations of the statoacoustic organ as known from other vertebrates is discussed.
Topics: Animals; Boidae; Ear; Semicircular Canals; Skull; Spiders
PubMed: 35969602
DOI: 10.1371/journal.pone.0262788 -
Scientific Reports Sep 2016The semicircular duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head...
The semicircular duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual semicircular duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the semicircular duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized duct system. We demonstrate the potential of these methods by presenting results for the duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies. Ariadne is freely available at http://www.earbank.org.
Topics: Animals; Biomechanical Phenomena; Ear, Inner; Humans; Imaging, Three-Dimensional; Macaca mulatta; Petrous Bone; Saimiri; Semicircular Ducts; Software; X-Ray Microtomography
PubMed: 27604473
DOI: 10.1038/srep32772 -
Seminars in Cell & Developmental Biology May 2017The vertebrate inner ear is a precision sensory organ, acting as both a microphone to receive sound and an accelerometer to detect gravity and motion. It consists of a... (Review)
Review
The vertebrate inner ear is a precision sensory organ, acting as both a microphone to receive sound and an accelerometer to detect gravity and motion. It consists of a series of interlinked, fluid-filled chambers containing patches of sensory epithelia, each with a specialised function. The ear contains many different differentiated cell types with distinct morphologies, from the flask-shaped hair cells found in thickened sensory epithelium, to the thin squamous cells that contribute to non-sensory structures, such as the semicircular canal ducts. Nearly all cell types of the inner ear, including the afferent neurons that innervate it, are derived from the otic placode, a region of cranial ectoderm that develops adjacent to the embryonic hindbrain. As the ear develops, the otic epithelia grow, fold, fuse and rearrange to form the complex three-dimensional shape of the membranous labyrinth. Much of our current understanding of the processes of inner ear morphogenesis comes from genetic and pharmacological manipulations of the developing ear in mouse, chicken and zebrafish embryos. These traditional approaches are now being supplemented with exciting new techniques-including force measurements and light-sheet microscopy-that are helping to elucidate the mechanisms that generate this intricate organ system.
Topics: Animals; Cell Differentiation; Cell Lineage; Cell Movement; Chick Embryo; Ectoderm; Epithelial Cells; Gene Expression Regulation, Developmental; Hair Cells, Auditory; Labyrinth Supporting Cells; Mice; Organogenesis; Species Specificity; Transcription Factors; Zebrafish
PubMed: 27686400
DOI: 10.1016/j.semcdb.2016.09.015 -
Development (Cambridge, England) May 2015Sensory hair cells are mechanoreceptors of the auditory and vestibular systems and are crucial for hearing and balance. In adult mammals, auditory hair cells are unable... (Review)
Review
Sensory hair cells are mechanoreceptors of the auditory and vestibular systems and are crucial for hearing and balance. In adult mammals, auditory hair cells are unable to regenerate, and damage to these cells results in permanent hearing loss. By contrast, hair cells in the chick cochlea and the zebrafish lateral line are able to regenerate, prompting studies into the signaling pathways, morphogen gradients and transcription factors that regulate hair cell development and regeneration in various species. Here, we review these findings and discuss how various signaling pathways and factors function to modulate sensory hair cell development and regeneration. By comparing and contrasting development and regeneration, we also highlight the utility and limitations of using defined developmental cues to drive mammalian hair cell regeneration.
Topics: Age Factors; Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Cycle; Cell Differentiation; Cell Lineage; Chick Embryo; Ear, Inner; Hair Cells, Ampulla; Lateral Line System; Mechanoreceptors; Mice; Models, Biological; Morphogenesis; Regeneration; Species Specificity; Zebrafish
PubMed: 25922522
DOI: 10.1242/dev.114926 -
Hearing Research Oct 2011Na(+) concentrations in endolymph must be controlled to maintain hair cell function since the transduction channels of hair cells are cation-permeable, but not... (Review)
Review
Na(+) concentrations in endolymph must be controlled to maintain hair cell function since the transduction channels of hair cells are cation-permeable, but not K(+)-selective. Flooding or fluctuations of the hair cell cytosol with Na(+) would be expected to lead to cellular dysfunction, hearing loss and vertigo. This review briefly describes cellular mechanisms known to be responsible for Na(+) homeostasis in each compartment of the inner ear, including the cochlea, saccule, semicircular canals and endolymphatic sac. The influx of Na(+) into endolymph of each of the organs is likely via passive diffusion, but these pathways have not yet been identified or characterized. Na(+) absorption is controlled by gate-keeper channels in the apical (endolymphatic) membrane of the transporting cells. Highly Na(+)-selective epithelial sodium channels (ENaCs) control absorption by Reissner's membrane, saccular extramacular epithelium, semicircular canal duct epithelium and endolymphatic sac. ENaC activity is controlled by a number of signal pathways, but most notably by genomic regulation of channel numbers in the membrane via glucocorticoid signaling. Non-selective cation channels in the apical membrane of outer sulcus epithelial cells and vestibular transitional cells mediate Na(+) and parasensory K(+) absorption. The K(+)-mediated transduction current in hair cells is also accompanied by a Na(+) flux since the transduction channels are non-selective cation channels. Cation absorption by all of these cells is regulated by extracellular ATP via apical non-selective cation channels (P2X receptors). The heterogeneous population of epithelial cells in the endolymphatic sac is thought to have multiple absorptive pathways for Na(+) with regulatory pathways that include glucocorticoids and purinergic agonists.
Topics: Animals; Cochlea; Ear, Inner; Endolymphatic Sac; Homeostasis; Humans; Ion Transport; Saccule and Utricle; Semicircular Canals; Sodium
PubMed: 21620939
DOI: 10.1016/j.heares.2011.05.003 -
Acta Otorhinolaryngologica Italica :... Dec 2019
Topics: Adult; Aged; Diagnostic Techniques, Otological; Female; Humans; Male; Meniere Disease; Middle Aged; Severity of Illness Index; Vestibule, Labyrinth; Young Adult
PubMed: 31950933
DOI: 10.14639/0392-100X-2461