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Current Topics in Developmental Biology 2015The perception of our environment via sensory organs plays a crucial role in survival and evolution. Hearing, one of our most developed senses, depends on the proper... (Review)
Review
The perception of our environment via sensory organs plays a crucial role in survival and evolution. Hearing, one of our most developed senses, depends on the proper function of the auditory system and plays a key role in social communication, integration, and learning ability. The ear is a composite structure, comprised of the external, middle, and inner ear. During development, the ear is formed from the integration of a number of tissues of different embryonic origin, which initiate in distinct areas of the embryo at different time points. Functional connections between the components of the hearing apparatus have to be established and maintained during development and adulthood to allow proper sound submission from the outer to the middle and inner ear. This highly organized and intimate connectivity depends on intricate spatiotemporal signaling between the various tissues that give rise to the structures of the ear. Any alterations in this chain of events can lead to the loss of integration, which can subsequently lead to conductive hearing loss, in case of outer and middle ear defects or sensorineural hearing loss, if inner ear structures are defective. This chapter aims to review the current knowledge concerning the development of the three ear compartments as well as mechanisms and signaling pathways that have been implicated in the coordination and integration process of the ear.
Topics: Animals; Ear; Ear, External; Ear, Middle; Epithelium; Hearing; Humans; Mesoderm; Models, Biological; Morphogenesis
PubMed: 26589927
DOI: 10.1016/bs.ctdb.2015.07.007 -
Indian Journal of Otolaryngology and... Aug 2022Endoscopic demonstration of the temporal bone and its related structures is a better tool specially for understanding the complex intricacies of the middle ear. In this...
Endoscopic demonstration of the temporal bone and its related structures is a better tool specially for understanding the complex intricacies of the middle ear. In this study we aim to understand the anatomy of the epitympanum/attic with the aid of Otoendoscopy using transmastoid and transattic approaches. Fifty four adult cadaveric temporal bones were dissected at our centre. Transcanal and transmastoid approaches were performed to visualize the middle ear spaces. We could demonstrate Cog, a ridge of bone that extends inferiorly from the tegmen plate just anterior to the head of malleus, epitympanic diaphragm by exploring the three malleal ligamental folds, Prussak's space and its boundaries, pathways of ventilation. Better understanding of the ventilation pathways of the middle ear, restoration of adequate air access in the attic help in better healing and prevent recurrences of diseases. Thus having a three dimentional orientation of the attic and its contents aid the surgeon in performing better surgery and thus provide disease free ear.
PubMed: 36032874
DOI: 10.1007/s12070-021-02389-z -
The Journal of the Acoustical Society... Apr 2021The mouse is an important animal model for hearing science. However, our knowledge of the relationship between mouse middle-ear (ME) anatomy and function is limited. The...
The mouse is an important animal model for hearing science. However, our knowledge of the relationship between mouse middle-ear (ME) anatomy and function is limited. The ME not only transmits sound to the cochlea in the forward direction, it also transmits otoacoustic emissions generated in the cochlea to the ear canal (EC) in the reverse direction. Due to experimental limitations, a complete characterization of the mouse ME has not been possible. A fully coupled finite-element model of the mouse EC, ME, and cochlea was developed and calibrated against experimental measurements. Impedances of the EC, ME, and cochlea were calculated, alongside pressure transfer functions for the forward, reverse, and round-trip directions. The effects on sound transmission of anatomical changes such as removing the ME cavity, pars flaccida, and mallear orbicular apophysis were also calculated. Surprisingly, below 10 kHz, the ME cavity, eardrum, and stapes annular ligament were found to significantly affect the cochlear input impedance, which is a result of acoustic coupling through the round window. The orbicular apophysis increases the delay of the transmission line formed by the flexible malleus, incus, and stapes, and improves the forward sound-transmission characteristics in the frequency region of 7-30 kHz.
Topics: Acoustic Stimulation; Acoustics; Animals; Cochlea; Ear, Middle; Mice; Round Window, Ear; Sound; Stapes
PubMed: 33940924
DOI: 10.1121/10.0004218 -
Wiley Interdisciplinary Reviews.... Mar 2019The evolution of the jaw represents a key innovation in driving the diversification of vertebrate body plans and behavior. The pharyngeal apparatus originated as gill... (Review)
Review
The evolution of the jaw represents a key innovation in driving the diversification of vertebrate body plans and behavior. The pharyngeal apparatus originated as gill bars separated by slits in chordate ancestors to vertebrates. Later, with the acquisition of neural crest, pharyngeal arches gave rise to branchial basket cartilages in jawless vertebrates (agnathans), and later bone and cartilage of the jaw, jaw support, and gills of jawed vertebrates (gnathostomes). Major events in the evolution of jaw structure from agnathans to gnathostomes include axial regionalization of pharyngeal elements and formation of a jaw joint. Hox genes specify the anterior-posterior identity of arches, and edn1, dlx, hand2, Jag1b-Notch2 signaling, and Nr2f factors specify dorsal-ventral identity. The formation of a jaw joint, an important step in the transition from an un-jointed pharynx in agnathans to a hinged jaw in gnathostomes involves interaction between nkx3.2, hand2, and barx1 factors. Major events in jaw patterning between fishes and reptiles include changes to elements of the second pharyngeal arch, including a loss of opercular and branchiostegal ray bones and transformation of the hyomandibula into the stapes. Further changes occurred between reptiles and mammals, including the transformation of the articular and quadrate elements of the jaw joint into the malleus and incus of the middle ear. Fossils of transitional jaw phenotypes can be analyzed from a developmental perspective, and there exists potential to use genetic manipulation techniques in extant taxa to test hypotheses about the evolution of jaw patterning in ancient vertebrates. This article is categorized under: Comparative Development and Evolution > Evolutionary Novelties Early Embryonic Development > Development to the Basic Body Plan Comparative Development and Evolution > Body Plan Evolution.
Topics: Animals; Biological Evolution; Chondrogenesis; Fishes; Jaw
PubMed: 30378758
DOI: 10.1002/wdev.337 -
Journal of Anatomy Feb 2016The anterior fixation of the anterior process of the malleus has been studied in a number of Cetartiodactyla. This anterior process, also known as processus gracilis, is... (Review)
Review
The anterior fixation of the anterior process of the malleus has been studied in a number of Cetartiodactyla. This anterior process, also known as processus gracilis, is provided by the prearticular (gonial), a dermal bone, whereas the cartilage of Meckel becomes resorbed in perinatal ontogenetic stages. Posteriorly, the prearticular fuses with the cartilaginous caput of the malleus; rostrally, the prearticular (= processus gracilis) is always fixed to the anterior crus of the ectotympanic by an extremely thin splint (thickness < 50 μm). From the rostral part of the processus gracilis all studied cetartiodactyls develop a processus internus of considerable size. This process was known as 'ossiculum accessorium mallei' in former times, and its homology has been disputed; from our microscopic-anatomical study we can definitely state that it is always a 'processus internus praearticularis'. This process contacts the fascia of the tensor tympani muscle. In non-ruminants, it articulates dorsally with the tegmen tympani and dorsolaterally with the ectotympanic; whereas the processus gracilis becomes more and more slender, the processus internus may grow to considerable size and normally is fused to the adjacent bones already in juveniles. However, in ruminants, the tegmen tympani tends to disappear and the processus internus praearticularis appears as relatively small bony knob at the floor of the medial cranial cavity, and it seems not to be fused to the surrounding bones; in later age stages, it may become secondarily overgrown by the petrosal. This dorsally exposed processus internus praearticularis seems to be a synapomorphy of the Ruminantia. The functional meaning of this internal process of the prearticular, which is also developed to a minor degree in Carnivora, remains unclear at the moment - but we present some speculations about this.
Topics: Animals; Malleus; Mammals; Ruminants; Swine
PubMed: 26510377
DOI: 10.1111/joa.12393 -
Otology & Neurotology : Official... Dec 2021Isolated malleus shaft fractures are rare cases. A commonly reported cause is a finger pulled out from a wet outer ear canal after a shower or bath. The objective was to...
BACKGROUND AND HYPOTHESIS
Isolated malleus shaft fractures are rare cases. A commonly reported cause is a finger pulled out from a wet outer ear canal after a shower or bath. The objective was to investigate experimentally the mechanism and forces needed to establish an isolated malleus shaft fracture.
METHODS
Ten fresh-frozen human temporal bones were adapted to allow visual inspection of the structures involved while negative pressure trauma was applied. Thirty malleus bones were broken and the required forces were measured. Measurements from 60 adult test subjects were used to create mathematical and physical models to calculate and measure the forces necessary for generating trauma. To calculate the maximum muscle force developed by the tensor tympani muscle, the muscle area and fiber type composition were determined.
RESULTS
The temporal bone experiments showed that applied negative pressure in a wet ear canal could not fracture the malleus shaft with only passive counterforce from supporting structures, although the forces exceeded what was required for a malleus shaft fracture. When adding calculated counteracting forces from the tensor tympani muscles, which consisted of 87% type II fibers, we estimate that a sufficient force is generated to cause a malleus fracture.
CONCLUSION
The combination of a negative pressure created by a finger pulling outward in a wet ear canal and a simultaneous counteracting reflexive force by the tensor tympani muscle were found to be sufficient to cause an isolated malleus fracture with an intact tympanic membrane.
Topics: Adult; Ear Canal; Humans; Malleus; Temporal Bone; Tensor Tympani; Tympanic Membrane
PubMed: 34353981
DOI: 10.1097/MAO.0000000000003306 -
Advances in Experimental Medicine and... 2019Bones contain spaces within them. The extraction and the analysis of those cavities are crucial in the study of bone tissue function and can inform about pathologies or...
Bones contain spaces within them. The extraction and the analysis of those cavities are crucial in the study of bone tissue function and can inform about pathologies or past traumatic events. The use of medical imaging techniques allows a non-invasive visualisation of skeletal cavities opening a new frontier in medical inspection and diagnosis. Here, we report the application of a new mesh-based approach for the isolation of skeletal cavities of different size and geometrical structure. We apply a mesh-based approach to extract (i) the main virtual cavities inside the human skull, (ii) a complete human endocast, (iii) the inner vasculature of the malleus bone and (iv) the medullary of a human femur. The detailed description of the mesh-based isolation method and its pioneristic application to four different case-studies show the potential of this approach in medical visualisation.
Topics: Anatomy; Bone and Bones; Data Visualization; Humans; Imaging, Three-Dimensional
PubMed: 31823241
DOI: 10.1007/978-3-030-24281-7_7 -
JPMA. the Journal of the Pakistan... Feb 2023To determine gender-based morphological variations in malleus.
OBJECTIVE
To determine gender-based morphological variations in malleus.
METHODS
The cross-sectional descriptive study was conducted at the Ear-Nose-Throat and Radiology departments of a public-sector hospital in Karachi, from January 20 to July 23, 2021, and comprised subjects of either gender aged 10-51 years who had intact ear ossicles. They were divided into equal male and female groups. After history and a thorough examination of the ear, high-resolution computed tomography scan of petrous temporal bone was done. The images were studied for malleus, to measure the parameters of its head width, length and shape of manubrium, and total length of malleus for possible morphological variations along gender lines. Data was analysed using SPSS 23.
RESULTS
Of the 50 subjects, 25(50%) were males with mean width of the head 3.04±0.34mm, mean length of manubrium 4.47±0.48mm, and mean total length of malleus 7.76±0.60mm. The corresponding values in 25(50%) females were 3.00±0.28mm, 4.31±0.45mm and 7.41±0.51mm. The total length of malleus between both genders was significantly different (p= 0.031). The shape of manubrium was straight in 10(40%) males and 8(32%) females, and curved in 15(60%) males and 17(68%) females.
CONCLUSIONS
Width of head, length of manubrium and total length of malleus were different in gender terms, but the total length of malleus was significantly different.
Topics: Female; Humans; Male; Malleus; Cross-Sectional Studies; Hospitals, Public; Public Sector; Social Group
PubMed: 36800718
DOI: 10.47391/JPMA.6307 -
Singapore Medical Journal Aug 2023A retrospective study (2011 to 2018) was conducted to evaluate the management of cholesteatomas with labyrinthine fistulae (LFs), clinical characteristics and...
INTRODUCTION
A retrospective study (2011 to 2018) was conducted to evaluate the management of cholesteatomas with labyrinthine fistulae (LFs), clinical characteristics and postoperative hearing outcomes in a hospital.
METHODS
Demographic data of patients with primary middle ear mastoidectomies for cholesteatoma were extracted. Preoperative high-resolution computed tomography (HRCT) temporal bone and intraoperative findings, and hearing levels preoperatively and postoperatively were evaluated.
RESULTS
Of the middle ear cholesteatomas, 15.6% (n = 14) of ears were complicated by LF. HRCT scans showed 92.9% sensitivity and 94.7% specificity in the identification of LFs. Intraoperative findings of LFs include stapes erosion (78.6%), malleus erosion (78.6%), incus erosion (92.9%), dehiscence of tegmen tympani (28.6%) and tympanic facial canal (64.3%). Compared to the non-LF group, the LF group showed significantly higher incidence of stapes erosion (P < 0.001), tegmen tympani dehiscence (P = 0.016) and semicircular canal dehiscence (P < 0.001). Matrix was removed completely in 85.7% (n = 12) and was left behind in 14.3% (n = 2) of ears. Also, 21.5% (n = 3) had preoperative dead ears. Postoperative hearing results had a mean follow-up time of 2.1 (standard deviation 1.5, range 0.14-4.84) years. In the matrix removal group (n = 9), 77.9% had unchanged hearing levels, 11.1% showed improvement and 11.1% showed decrease in hearing levels. The matrix preservation group (n = 2) had deteriorated hearing levels.
CONCLUSION
Preservation of hearing in LFs is possible with cautious matrix removal. Despite matrix preservation to preserve hearing in large LFs, our patients' hearing deteriorated postoperatively. Longer follow-up of hearing with matrix preservation may show poorer hearing outcomes.
PubMed: 37675676
DOI: 10.4103/singaporemedj.SMJ-2021-377 -
Science Advances Sep 2015Studies of sensory capacities in past life forms have offered new insights into their adaptations and lifeways. Audition is particularly amenable to study in fossils...
Studies of sensory capacities in past life forms have offered new insights into their adaptations and lifeways. Audition is particularly amenable to study in fossils because it is strongly related to physical properties that can be approached through their skeletal structures. We have studied the anatomy of the outer and middle ear in the early hominin taxa Australopithecus africanus and Paranthropus robustus and estimated their auditory capacities. Compared with chimpanzees, the early hominin taxa are derived toward modern humans in their slightly shorter and wider external auditory canal, smaller tympanic membrane, and lower malleus/incus lever ratio, but they remain primitive in the small size of their stapes footplate. Compared with chimpanzees, both early hominin taxa show a heightened sensitivity to frequencies between 1.5 and 3.5 kHz and an occupied band of maximum sensitivity that is shifted toward slightly higher frequencies. The results have implications for sensory ecology and communication, and suggest that the early hominin auditory pattern may have facilitated an increased emphasis on short-range vocal communication in open habitats.
PubMed: 26601261
DOI: 10.1126/sciadv.1500355