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Journal of Anatomy Apr 2022Based on high-resolution computed tomography, we describe in detail the petrosal and inner ear anatomy of one of the few known African stem paenungulates...
Based on high-resolution computed tomography, we describe in detail the petrosal and inner ear anatomy of one of the few known African stem paenungulates (Paenungulatomorpha), Ocepeia daouiensis from the Selandian of the Ouled Abdoun phosphate basin (Morocco). The petrosal of Ocepeia displays some remarkable, probably derived features (among eutherians) such as relatively small pars cochlearis, pars canalicularis labyrinth (including small semicircular canals), a large wing-like pars mastoidea, a large and inflated tegmen tympani, and the dorsoventral orientation of the large canal for the ramus superior. The presence of small semicircular canals in Ocepeia is an interesting shared trait with tenrecoidean afrotherians. Otherwise, and consistent with a general primitive skull morphology, the middle ear and labyrinth of Ocepeia daouiensis is characterised by many plesiomorphic traits close to the eutherian generalised plan. This adds to the rather generalised morphology of the earliest crown paenungulates such as Eritherium, Phosphatherium and Seggeurius to support an ancestral paenungulatomorph morphotype poorly derived from the eutherian pattern. As a result, Ocepeia provides key morphological and fossil data to test phylogenetic relationships of the Afrotheria (including Paenungulatomorpha) at the placental root mostly inferred from molecular studies.
Topics: Animals; Ear, Inner; Female; Fossils; Mammals; Morocco; Phylogeny; Placenta; Pregnancy
PubMed: 32735727
DOI: 10.1111/joa.13255 -
Journal of Anatomy Mar 2022The semicircular canals (SCCs) transduce angular acceleration of the head into neuronal signals, and their morphology has been used to infer function. Once formed, the...
The semicircular canals (SCCs) transduce angular acceleration of the head into neuronal signals, and their morphology has been used to infer function. Once formed, the bony labyrinth, that surrounds the canals, is tightly regulated and has a very low bone turnover. However, relaxed postnatal inhibition of bone remodelling later in ontogeny may allow for some organised adjustments of shape and size or for greater stochastic variation. In the present study, we test the hypotheses that after birth, the shape and size of the bony canal changes or becomes more variable, or both. We study microCT scans of human perinatal and adult temporal bones using a combination of geometric morphometric analysis and cross-sectional measures. Results revealed marginal differences of size (<5%), of cross-sectional shape and of measurement variability. Geometry of the three canals together and their cross-sectional areas were, however, indistinguishable between perinates and adults. These mixed findings are indicative of diminutive levels of relaxed inhibition superimposed over a constrained template of SCC morphology.
Topics: Adult; Humans; Semicircular Canals; Temporal Bone; X-Ray Microtomography
PubMed: 34674260
DOI: 10.1111/joa.13576 -
PloS One 2018The semicircular canal (SC) system of the inner ear detects head angular accelerations and is essential for navigation and spatial awareness in vertebrates. Because the...
The semicircular canal (SC) system of the inner ear detects head angular accelerations and is essential for navigation and spatial awareness in vertebrates. Because the bony labyrinth encloses the membranous labyrinth SCs, it can be used as a proxy for animal behavior. The bony labyrinth of dicynodonts, a clade of herbivorous non-mammalian synapsids, has only been described in a handful of individuals and remains particularly obscure. Here we describe the bony labyrinth anatomy of three Endothiodon cf. bathystoma specimens from Mozambique based on digital reconstructions from propagation phase-contrast synchrotron micro-computed tomography. We compare these findings with the bony labyrinth anatomy of their close relative Niassodon. The bony labyrinths of Endothiodon and Niassodon are relatively similar and show only differences in the shape of the horizontal SCs and the orientation of the vertical SCs. When compared to extant mammals, Endothiodon and Niassodon have highly eccentric SCs. In addition, the Endothiodon SCs are nearly orthogonal. An eccentric and orthogonal SC morphology is consistent with a specialization in rapid head movements, which are typical of foraging or feeding behaviors. Furthermore, we estimate the body mass of these Endothiodon specimens at ~116 to 182 kg, based on the average SC radii calculated using a linear regression model optimized by the Amemiya Prediction Criterion. Our findings provide novel insights into the paleobiology of Endothiodon which are consistent with the peculiar feeding mechanism among dicynodonts presumed from their multiple postcanine toothrows.
Topics: Anatomic Variation; Animals; Biological Evolution; Body Size; Ear, Inner; Fossils; Image Processing, Computer-Assisted; Mozambique; Species Specificity; Vertebrates; X-Ray Microtomography
PubMed: 29538421
DOI: 10.1371/journal.pone.0189883 -
Hearing Research Mar 2011The frog inner ear contains three regions that are sensitive to airborne sound and which are functionally distinct. (1) The responses of nerve fibres innervating the... (Comparative Study)
Comparative Study Review
The frog inner ear contains three regions that are sensitive to airborne sound and which are functionally distinct. (1) The responses of nerve fibres innervating the low-frequency, rostral part of the amphibian papilla (AP) are complex. Electrical tuning of hair cells presumably contributes to the frequency selectivity of these responses. (2) The caudal part of the AP covers the mid-frequency portion of the frog's auditory range. It shares the ability to generate both evoked and spontaneous otoacoustic emissions with the mammalian cochlea and other vertebrate ears. (3) The basilar papilla functions mainly as a single auditory filter. Its simple anatomy and function provide a model system for testing hypotheses concerning emission generation. Group delays of stimulus-frequency otoacoustic emissions (SFOAEs) from the basilar papilla are accounted for by assuming that they result from forward and reverse transmission through the middle ear, a mechanical delay due to tectorial membrane filtering and a rapid forward and reverse propagation through the inner ear fluids, with negligible delay.
Topics: Animals; Anura; Biomechanical Phenomena; Ear, Inner; Evoked Potentials, Auditory; Hearing; Sensory Receptor Cells
PubMed: 20149854
DOI: 10.1016/j.heares.2010.02.004 -
HNO Jun 2019In several systems of the body (muscle, liver, nerves), new studies have examined the internal structure of mitochondria and brought to light striking new findings about... (Review)
Review
In several systems of the body (muscle, liver, nerves), new studies have examined the internal structure of mitochondria and brought to light striking new findings about how mitochondria are constructed and how their structure affects cell function. In the inner ear field, however, we have little structural knowledge about hair cell and supporting cell mitochondria, and virtually none about mitochondrial subtypes or how they function in health and disease. The need for such knowledge is discussed in this short review.
Topics: Cochlea; Ear, Inner; Hair; Hair Cells, Auditory; Humans; Mitochondria
PubMed: 30969353
DOI: 10.1007/s00106-019-0662-2 -
Anatomical Record (Hoboken, N.J. : 2007) May 2022The inner ear contains the end organs for balance (vestibular labyrinth) and hearing (cochlea). The vestibular labyrinth is comprised of the semicircular canals...
The inner ear contains the end organs for balance (vestibular labyrinth) and hearing (cochlea). The vestibular labyrinth is comprised of the semicircular canals (detecting angular acceleration) and otolith organs (utricle and saccule, which detect linear acceleration and head tilt relative to gravity). Lying just inferior to the utricle is the membranous membrana limitans (ML). Acting as a keystone to vestibular geometry, the ML provides support for the utricular macula and acts as a structural boundary between the superior (pars superior) and inferior (pars inferior) portions of the vestibular labyrinth. Given its importance in vestibular form, understanding ML morphology is valuable in establishing the spatial organization of other vestibular structures, particularly the utricular macula. Knowledge of the 3D structure and variation of the ML, however, remain elusive. Our study addresses this knowledge gap by visualizing, in 3D, the ML and surrounding structures using micro-CT data. By doing so, we attempt to clarify: (a) the variation of ML shape; (b) the reliability of ML attachment sites; and (c) the spatial relationship of the ML to the stapes footplate using landmark-based Generalized Procrustes, Principal Component and covariance analyses. Results indicate a consistent configuration of three distinct bony ML attachments including an anterolateral, medial, and posterior attachment which all covary with bony structure. Our results set the stage for further understanding into vestibular and more specifically, utricular macula spatial configuration within the human head, offering the potential to aid in clinical and evolutionary studies which rely on a 3D understanding of vestibular spatial configuration.
Topics: Biological Evolution; Humans; Imaging, Three-Dimensional; Reproducibility of Results; Semicircular Canals; Vestibule, Labyrinth
PubMed: 34021723
DOI: 10.1002/ar.24675 -
Journal of Anatomy Feb 2017Foetuses are a source of scientific information to understand the development and evolution of anatomical structures. The bony labyrinth, surrounding the organ of...
Foetuses are a source of scientific information to understand the development and evolution of anatomical structures. The bony labyrinth, surrounding the organ of balance and hearing, is a phylogenetically and ecologically informative structure for which still little concerning growth and shape variability is known in many groups of vertebrates. Except in humans, it is poorly known in many other placentals and its prenatal growth has almost never been studied. Ruminants are a diversified group of placentals and represent an interesting case study to understand the prenatal growth of the ear region. We computed tomography -scanned five cow foetuses and an adult petrosal bone (Bos taurus, Artiodactyla, Mammalia), and describe the bony labyrinth when already ossified. The foetuses encompass the second half of the 9.3-month-long gestation period of the cow. They were sampled at different ontogenetic stages to understand how and when the petrosal bone and bony labyrinth ossify in ruminants. The petrosal bone and bony labyrinth ossify within about 20 days in the fourth month of gestation. The bony labyrinth is already fully ossified at least in the 6th month, while only the cochlea, most of the vestibule and the common crus are already ossified at the beginning of the 4th month. The pars canalicularis of the petrosal thus ossifies at last. The size and volume of the bony labyrinth stay similar from the 6th month (possibly even from the 5th). From the end of the 4th month of gestation, a progressive lengthening of the cochlear aqueduct and endolymphatic sac occurs, culminating in the adult form and partly explaining the larger volume of the later. The inner ear in the cow ossifies quickly during the gestation period, being fully ossified around mid-gestation time, as in humans. The adult size and most of its volume are reached by mid-gestation time while the petrosal bone and skull still grow. A negative ontogenetic allometry between the bony labyrinth and the petrosal bone and skull is thus observed. It matches the evolutionary negative allometry of the structure observed in earlier studies. Few changes occur after ossification is achieved; only open structures (i.e. cochlear aqueduct and endolymphatic sac) continue to grow after birth and reflect size increase of the petrosal bone.
Topics: Animals; Cattle; Ear, Inner; Petrous Bone; Ruminants
PubMed: 27726136
DOI: 10.1111/joa.12549 -
Journal of the Association For Research... Feb 2020This study aims to document the historical conceptualization of the inner ear as the anatomical location for the appreciation of sound at a continuum of frequencies and... (Review)
Review
This study aims to document the historical conceptualization of the inner ear as the anatomical location for the appreciation of sound at a continuum of frequencies and to examine the evolution of concepts of tonotopic organization to our current understanding. Primary sources used are from the sixth century BCE through the twentieth century CE. Each work/reference was analyzed from two points of view: to understand the conception of hearing and the role of the inner ear and to define the main evidential method. The dependence on theory alone in the ancient world led to inaccurate conceptualization of the mechanism of hearing. In the sixteenth century, Galileo described the physical and mathematical basis of resonance. The first theory of tonotopic organization, advanced in the seventeenth century, was that high-frequency sound is mediated at the apex of the cochlea and low-frequency at the base of the cochlea. In the eighteenth and nineteenth centuries, more accurate anatomical information was developed which led to what we now know is the accurate view of tonotopic organization: the high-frequency sound is mediated at the base and low-frequency sound at the apex. The electrical responses of the ear discovered in 1930 allowed for physiological studies that were consistent with the concept of a high to low tone sensitivity continuum from base to apex. In the mid-twentieth century, physical observations of models and anatomical specimens confirmed the findings of greater sensitivity to high tones at the base and low tones at the apex and, further, demonstrated that for high-intensity sound, there was a spread of effect through the entire cochlea, more so for low-frequency tones than for high tones. Animal and human behavioral studies provided empirical proof that sound is mediated at a continuum of frequencies from high tones at the base through low tones at the apex of the cochlea. Current understanding of the tonotopic organization of the inner ear with regard to pure tones is the result of the acquisition over time of knowledge of acoustics and the anatomy, physical properties, and physiology of the inner ear, with the ultimate verification being behavioral studies. Examination of this complex evolution leads to understanding of the way each approach and evidential method through time draws upon previously developed knowledge, with behavioral studies providing empirical verification.
Topics: Anatomy; Animals; Ear, Inner; Hearing; History, 16th Century; History, 17th Century; History, 18th Century; History, 19th Century; History, 20th Century; History, Ancient; Humans; Physiology
PubMed: 32020418
DOI: 10.1007/s10162-019-00741-3 -
Physiological Research Nov 2020Sensorineural hearing loss and vertigo, resulting from lesions in the sensory epithelium of the inner ear, have a high incidence worldwide. The sensory epithelium of the... (Review)
Review
Sensorineural hearing loss and vertigo, resulting from lesions in the sensory epithelium of the inner ear, have a high incidence worldwide. The sensory epithelium of the inner ear may exhibit extreme degeneration and is transformed to flat epithelium (FE) in humans and mice with profound sensorineural hearing loss and/or vertigo. Various factors, including ototoxic drugs, noise exposure, aging, and genetic defects, can induce FE. Both hair cells and supporting cells are severely damaged in FE, and the normal cytoarchitecture of the sensory epithelium is replaced by a monolayer of very thin, flat cells of irregular contour. The pathophysiologic mechanism of FE is unclear but involves robust cell division. The cellular origin of flat cells in FE is heterogeneous; they may be transformed from supporting cells that have lost some features of supporting cells (dedifferentiation) or may have migrated from the flanking region. The epithelial-mesenchymal transition may play an important role in this process. The treatment of FE is challenging given the severe degeneration and loss of both hair cells and supporting cells. Cochlear implant or vestibular prosthesis implantation, gene therapy, and stem cell therapy show promise for the treatment of FE, although many challenges remain to be overcome.
Topics: Animals; Ear, Inner; Epithelial-Mesenchymal Transition; Epithelium; Hair Cells, Auditory, Inner; Hearing Loss, Sensorineural; Humans; Noise
PubMed: 32901490
DOI: 10.33549/physiolres.934447 -
La Radiologia Medica Oct 2021In the multidisciplinary management of patients with inner ear malformations (IEMs), the correct diagnosis makes the differences in terms of clinical and surgical... (Review)
Review
In the multidisciplinary management of patients with inner ear malformations (IEMs), the correct diagnosis makes the differences in terms of clinical and surgical treatment. The complex anatomical landscape of the inner ear, comprising several small structures, makes imaging of this region particularly challenging for general radiologists. Imaging techniques are important for identifying the presence and defining the type of IEM and the cochlear nerve condition. High-resolution magnetic resonance imaging (MRI) sequences and high-resolution computed tomography (HRCT) are the mainstay imaging techniques in this area. Dedicated MRI and HRCT protocols play an important role in the diagnosis and treatment of patients with inner ear disease. The most suitable technique should be selected depending on the clinical setting. However, in cases of congenital malformation of the inner ear, these techniques should be considered complementary. Since prompt intervention has a positive impact on the treatment outcomes, early diagnosis of IEMs is very important in the management of deaf patients. This article reviews the key concepts of IEMs for clinical radiologists by focusing on recent literature updates, discusses the principal imaging findings and clinical implications for every IEM subgroup, thus providing a practical diagnostic approach.
Topics: Ear, Inner; Humans; Magnetic Resonance Imaging; Tomography, X-Ray Computed
PubMed: 34196909
DOI: 10.1007/s11547-021-01387-z