Ears
Marie Lyons, Arvind Singh in Your First ENT Job, 2018
The external ear consists of the pinna and the outer ear canal (seeFigure 1.1). The outer third of the ear canal is cartilaginous, hair-bearing and wax-producing. It is also not particularly sensitive, which makes it relatively easy to inspect with an auroscope. The inner third is bony and exquisitely sensitive. Push too deep into the bony ear canal and the patient will certainly protest! The outer ear canal ends at the eardrum, which in a healthy ear is a pale grey structure (seeFigure 1.2). The most obvious features are the handle of the malleus and antero-inferiorly the cone of light (see below). When you are shown a picture of the eardrum you can always identify which side it is on by the direction in which the malleus is pointing. If the eardrum is on the right side, the malleus will point upwards and superiorly to the right from the middle of the eardrum. If it is on the left side, the malleus will point to the left (amaze your boss at quizzes!).
Hearing Aids and Auditory Rehabilitation
R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne in Scott-Brown's Essential Otorhinolaryngology, 2022
Most hearing aids also include a wireless receiver so that audio signals can be input to the device from a mobile phone or other streaming device, a remotely located microphone (such as worn by a teacher in a classroom) and/or a hearing aid on the other side of the head. The most common style of hearing aids is behind the ear (BTE), where either the entire hearing aid, or all the components except the receiver, are positioned between the pinna and the head surface. They connect to the ear canal via a sound tube, or via thin wires when the receiver is in the ear canal. The end of the tube or the receiver are held in place in the ear canal by either a custom-shaped ear mould, or a compliant tip that deforms to match the cross-sectional shape of the ear canal. Alternative styles include in the ear, in the canal and completely in the-canal. While the latter two styles have slight cosmetic advantages over BTE devices, BTEs can contain directional microphones, which offer performance in noise that the canal-style devices cannot match. Much less commonly, a contralateral routing of signals (CROS) hearing aid is used to pick up sounds from the side of the head with a completely deaf ear, and play an amplified version of it to the other ear.
Mouth and throat, face, and the five senses
Frank J. Dye in Human Life Before Birth, 2019
To perceive vibrations propagated through the air, natural selection has provided us with a high-fidelity, stereophonic receiver, comprising our ears and brain. Sound waves, gathered into our external ear canals by the pinnae, cause first our eardrums and then our middle ear ossicles to vibrate, setting in motion fluid movement in the cochlea of the inner ear. This movement causes stereocilia in the cochlea to bend, resulting in a train of nerve impulses being sent (via cranial nerve VIII) to the brain, which interprets the impulses as sound. In addition, the inner ears possess systems of semicircular canals. These canals allow us to sense our position in space, and consequently maintain balance as we go about our various activities, by detecting fluid motion in three axes (x, y, and z) (Figure 17.8).
Prevention of progressive hearing loss in a mouse model of diabetes by oral intake of eicosapentaenoic acid ethyl ester
Published in Acta Oto-Laryngologica, 2023
Takafumi Matsuura, Kazuma Sugahara, Yohei Yamamoto, Junko Tsuda, Makoto Hashimoto, Hiroshi Yamashita
Auditory brainstem responses (ABRs) were measured using electrophysiological auditory tests to evaluate auditory function in mice. ABRs were recorded after general anesthesia by intraperitoneal administration of a mixture of medetomidine hydrochloride (0.3 mg/kg, Nippon Zenyaku Kogyo, Fukushima, Japan), midazolam (4mg/kg; Astellas Pharma, Tokyo, Japan), and butorphanol tartrate (5 mg/kg; Meiji Seika Pharma, Tokyo, Japan). For auditory stimulation, an earphone was inserted into the ear canal. Auditory stimuli consisted of 4, 8, 16, and 32 kHz tone bursts (rise-fall time, 2 ms; duration, 4 ms). Using platinum needle electrodes, positive electrodes were inserted under the skin of the right temporal region, negative electrodes in the left temporal region, and ground electrodes in the trunk, and responses were recorded. The number of stimuli was 256, and responses were recorded using a high-frequency auditory signal processor (RZ6, Tucker-Davis Technologies, Gainesville, FL). The stimulus rate was 21/s, period was 47.619/ms and time window was 10 ms. All were 100 Hz high-pass, 5 kHz low-pass, and 60 Hz notch filtered. The lowest stimulus for which wave 1 of the ABR waveform could be confirmed was defined as the ABR threshold. After the measurement was completed, the mice were injected intraperitoneally with atipamezole hydrochloride (3 mg/kg; Nippon Zenyaku Kogyo, Fukushima, Japan) and awakened.
Predicting children’s real-ear-to-coupler differences based on tympanometric data
Published in International Journal of Audiology, 2023
Ryan W. McCreery, Jeffery Crukley, Anastasia Grindle, Gabrielle R. Merchant, Elizabeth Walker
Equivalent ear-canal volume measured during tympanometry is different than the residual ear-canal volume that occurs with coupling to an earmold, which could increase the variability of the immittance-predicted RECD. Additionally, the 226 Hz tympanometry data that were incorporated into the immittance-predicted RECD model characterises the outer and middle ear at a single, low frequency. As noted above, the immittance-predicted RECD model performed most poorly at 6000 Hz. The RECD is a broadband measurement and may benefit from the use of a broadband measure of outer and middle ear immittance using available techniques such as wideband acoustic immittance. Tympanometry also pressurises the ear canal to characterise the admittance and relative pressure of the middle ear, but RECD measurements are not completed under pressurised conditions. Pressurising the ear canal can influence the acoustic characteristics and sound level in the ear canal. Wideband acoustic immittance can be conducted at ambient pressure like the RECD and may more accurately predict the RECD. Future research should consider the impact of unpressurised wideband acoustic immittance estimates of outer and middle ear function to determine if further improvements in RECD prediction can be achieved.
Effect of ossicular chain deformity on reverse stimulation considering the overflow characteristics of third windows
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Houguang Liu, Lin Xue, Jianhua Yang, Gang Cheng, Lei Zhou, Xinsheng Huang
To simulate the structural abnormalities of the ossicular chain, we used our previously reported FE model including the ear canal and middle ear (Zhou et al. 2016). In brief, the geometric model of the ear canal and middle ear are based on a series of histological section images collected from a human temporal bone (male, 60 years old, right ear). The volume of the air in the ear canal is 952.18 mm3, and the average length is about 26.32 mm. The volume of the malleus, incus, and stapes are 13.53, 15.54, and 2.95 mm3, respectively. The corresponding mass can be calculated from the measured dimensions. The definition of fluid-structure interaction surface, boundary conditions, and material properties of components in the model are consistent with those reported by Zhou et al. (2016). Figure 2 indicates the FE model of the ear canal and the middle ear. Coupled structural–acoustic analysis of the FE model was conducted using Abaqus (Dassault Systèmes, Johnston, RI, USA).