The Anatomy of Hearing
James R. Tysome, Rahul G. Kanegaonkar in Hearing, 2015
The ear is divided into three separate but functionally related subunits. The outer ear consists of the pinna and external auditory canal (EAC) bounded medially by the lateral surface of the tympanic membrane (TM). The middle ear contains the ossicular chain, which spans the middle ear cleft and allows acoustic energy to be transferred from the TM to the oval window and then into the cochlea of the inner ear. The EAC is a tortuous passage approximately 2.5 cm in length that directs sound from the conchal bowl to the TM. The squamous epithelium of the TM and ear canal is unique and is worthy of consideration. The inner ear is comprised of the cochlea and the peripheral vestibular apparatus. While the peripheral vestibular apparatus is dedicated to detecting angular and linear acceleration and static head tilt, the cochlea is devoted to hearing.
Conductive mechanism
Stanley A. Gelfand in Hearing, 2017
The pinna influences localization because its depressions and ridges filter the high-frequency aspects of the signal in a way that depends on the direction of the sound. Pinna effects are particularly important when one must localize sounds while listening with only one ear, because monaural hearing precludes the use of the interaural differences available during binaural hearing, and when the sound source is in the medial plane of the head, where interaural differences are minimized because the sound source is equidistant from both ears. The tympanic membrane is located at the end of the ear canal rather than flush with the surface of the skull. Sounds reaching the eardrum are thus affected by the acoustic characteristics of the ear canal. The right ear is the near ear when the sound comes from the right, and it is the far ear when the sound comes from the left.
The ear
Rogan J Corbridge in Essential ENT, 2011
The external ear is made up of the auricle or pinna and the external auditory meatus (EAM). Its function is to collect and transmit sound to the tympanic membrane. The nerve supply of the external ear is surprisingly complex. The skin of the lateral surface of the tympanic membrane and ear canal is unusual. Ear wax blocking the EAM is probably the most common ear problem in the general population. Wax-softening agents such as sodium bicarbonate ear drops are the first line of treatment. Ear syringing involves flushing the ear with warm water to wash out any wax or debris. Scratching the ear canal with a fingernail or cotton-bud causes local trauma and allows a portal of entry for infection, with further inflammation. Knowledge of the nerve supply of the ear is important as patients may present with otalgia referred to the ear by stimulation of these nerves elsewhere in their course.
Histologic changes of mesenchymal stem cell repair of tympanic membrane perforation
Published in Acta Oto-Laryngologica, 2017
Stefania Goncalves, Esperanza Bas, Michael Langston, Ariel Grobman, Bradley J. Goldstein, Simon Angeli
Conclusion: Mesenchymal stem-cells are good candidates for cell-therapy of chronic tympanic membranes perforations. Objectives: To determine the effects of cell-based therapy in tympanic membrane perforations. Methods: Young C57BL/6 mice were anesthetized with intraperitoneal administration of ketamine and xylazine and randomly divided into three groups (n = 4 ears/group) that underwent bilateral sub-total pars tensa perforations of equal sizes using a sterile 27-gauge needle under a surgical microscope. Six-to-eight hours after injury, one group of mice did not receive treatment (acute perforation control), and the last two groups were treated with BM-MSCs embedded within HA scaffolds previously soaked in PBS to rinse culture media residues to avoid confounders and were euthanized 1 or 2 weeks after treatment. Results: Untreated tympanic membrane perforations developed a hyper-cellular infiltrate surrounding the injury site, while BM-MSC treated eardrums showed a reduced inflammatory response after the first week and a restoration of the trilaminar configuration 2 weeks after treatment, mimicking a normal tympanic membrane.
Fatigue analysis of tympanic membrane after ossiculoplasty
Published in Acta Oto-Laryngologica, 2017
Lei Zhou, Miaolin Feng, Xinsheng Huang, Maoli Duan
Conclusion: A tentative conclusion was made that the finite element method can be used to investigate the fatigue life of the tympanic membrane after ossiculoplasty; the main reason of the extrusion of the tympanic membrane may not be blamed to the fatigue mechanism under normal sound pressure. Objective: This study was to investigate the extrusion of the prosthesis from the tympanic membrane at post-ossiculoplasty by finite element method. Methods: A finite element model of the human middle ear has been constructed and used as the model of the constructed middle ear at post-ossiculoplasty. Then the fatigue life of the tympanic membrane was calculated under different sound pressure level using this model. Results: The tympanic membrane would not be extruded under normal sound pressure level. The sound pressure level which caused the tympanic membrane to crack in less than 3 years was higher than 145.17 dB (362.5 Pa).
The effect of platelet-rich fibrin membrane on the repair of perforated tympanic membrane: an experimental study
Published in Acta Oto-Laryngologica, 2017
Nuray Ensari, Özer Erdem Gür, Mehmet Türker Öztürk, Dinç Süren, Ömer Tarık Selçuk, Üstün Osma
Conclusion: Platelet-rich fibrin (PRF) membrane could be used successfully in the repair of tympanic membrane perforation and wound healing. Objectives: To evaluate the effect of platelet-rich fibrin membrane in the repair of perforated tympanic membrane. Methods: After otoscopic examination, a 3-mm perforation was made in the posterior quadrant of both tympanic membranes of 50 adult male Sprague-Dawley rats. Venous blood was withdrawn from the rats, then centrifuged. PRF was obtained in membrane form. The membrane was placed on the right tympanic membrane perforation. The perforations on the left side were left to spontaneously heal and, thus, formed the control group. Daily examinations were made of 20 rats and the time to healing of the tympanic membrane was recorded. The remaining 30 rats were separated into five groups of six, and histopathological examination was made. Evaluation was made in respect of the presence of oedema in the lamina propria, neovascularization, fibroblastic reaction, and inflammatory cells. Results: The healing time of the tympanic membrane perforation was determined as mean 10.3 ± 2.18 days in the study group applied with PRF and 17 ± 2.40 days in the control group. Higher values in respect of fibrosis and neovascularization were obtained in the study group.
Related Knowledge Centers
- Ear Canal
- External Ear
- Middle Ear
- Mucosa
- Outer Ear
- Ear Auricle
- External Ear Canal