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Frontiers in Bioengineering and... 2022The middle ear is part of the ear in all terrestrial vertebrates. It provides an interface between two media, air and fluid. How does it work? In mammals, the middle ear... (Review)
Review
The middle ear is part of the ear in all terrestrial vertebrates. It provides an interface between two media, air and fluid. How does it work? In mammals, the middle ear is traditionally described as increasing gain due to Helmholtz's hydraulic analogy and the lever action of the malleus-incus complex: in effect, an impedance transformer. The conical shape of the eardrum and a frequency-dependent synovial joint function for the ossicles suggest a greater complexity of function than the traditional view. Here we review acoustico-mechanical measurements of middle ear function and the development of middle ear models based on these measurements. We observe that an impedance-matching mechanism (reducing reflection) rather than an impedance transformer (providing gain) best explains experimental findings. We conclude by considering some outstanding questions about middle ear function, recognizing that we are still learning how the middle ear works.
PubMed: 36299283
DOI: 10.3389/fbioe.2022.983510 -
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