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Results for “TENSOR TYMPANI”

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At least 289 records · Page 16Linked to original sources
PubMed1990

The morphometry and three-dimensional structure of the adult eustachian tube: implications for function.

An accurate description of the functioning Eustachian tube (ET) requires a thorough knowledge of the anatomic relationships of its components. To this end, 15 "normal" adult ETs were obtained, sectioned, and stained with hemotoxylin-eosin. Descriptive and quantitative data of ET structures and their relationships were obtained. Eustachian tube length was normalized and comparisons between specimens made. This analysis suggests (1) in its midsection the cartilage is loosely attached to the cranial base; (2) the deep portion of the tensor veli palatini (TVP) originates from the lateral lamina and the fibrous portion of the lateral membraneous wall; and (3) the levator veli palatini (LVP) can interact with the ET primarily via the elongated medial lamina in the anterior portion of the ET. These observations suggest the ET is opened by a medial rotation of cartilage effected primarily by the TVP, but aided anteriorly by the LVP.

Adipose Tissue↗
PubMed1975

Cochlear action potentials in experimentally induced hypothyroidism in guinea pigs.

Hypothyroidism was induced in guinea pigs by various methods. Using a new technique, electrodes were permanently implanted and action potentials aroused by different sound stimuli recorded and measured. The results obtained before and during the hypometabolic state were analysed and compared with those obtained after replacement therapy. A tentative attempt was made to extrapolate the changes in pattern and magnitude of the action potentials caused by the experimentally induced hypothyroidism, to the hearing disorders observed in patients with thyroid deficiency.

Acoustic Stimulation↗
PubMedDate not supplied

Holographic vibration analysis of the ossicular chain.

The mechanics of movement of the ossicular chain has been investigated on human temporal bone preparations by means of time average holography. The malleus and incus moved like a lever around an axis, which position was somewhat dependent upon frequency. Simulation of contraction of the muscles of the middle ear gave as result a change in the pattern of movement of the ossicular chain. The position of the rotatory axis was changed, and the amplitudes of vibration were reduced. This should be a protecting mechanism.

Autopsy↗
PubMedDate not supplied

Volume displacement of the tympanic membrane in the sitting position as a function of middle ear muscle activity. A quantitative microflow method.

An open microflow meter system has been worked out for quantitative recording of the volume displacement of the tympanic membrane and its movement direction at stapedius reflex. An acoustically elicited M. stapedius contraction can be recognized by the characteristic response and latency time. The stapedius reflex contraction causes an outward or inward movement of the tympanic membrane. The magnitude of the volume displacement of the tympanic membrane is influenced by the middle ear pressure and in some ears the movement direction of the tympanic membrane changes.

Adult↗
PubMedDate not supplied

Effect of the acoustic reflex on inner ear damage induced by industrial noise.

Shipyard noise is a variable noise which induces permanent threshold shift (PTS) in exposed workers. In humans, the stapedius reflex has been found to be very stable in this type of exposure. Temporary threshold shift (TTS) in the absence of stapedius reflex has been found to extend downwards through the speech-frequencies instead of showing a high frequency dip as when the stapedius reflex is normal. The features of PTS produced by the same type of noise was investigated in rabbits with and without functioning middle ear muscles. The auditory sensitivity was measured by auditory brain stem response (ABR) and by the stapedius reflex response. Middle ear muscle function was blocked by denervation of the stapedius muscle or by general anesthesia. With normal middle ear reflex very little PTS was found. When the muscles were inactivated during the noise exposure the PTS was very extensive and covered the mid frequency range. On the basis of previous findings in humans and the present animal study it is suggested that the features of the stapedius reflex should be considered both in assessment of individual susceptibility and design of optimal acoustic environments.

Animals↗
PubMed1988

The mechanics of the middle-ear at static air pressures: the role of the ossicular joints, the function of the middle-ear muscles and the behaviour of stapedial prostheses.

In an experimental study, the mechanical behaviour of the ossicle-chain during changes of the static air pressure was analyzed microscopically and with a radiographic magnification technique in temporal bone preparations. Several preliminary experiments served to pinpoint methodological problems, like exsiccation-artifacts, storage procedures, preparation defects, missing air-cushion effect with the opened middle-ear cavity, absent labyrinthine pressure, relation of the optical axis to middle-ear structures and statistical reproducibility of the measured values. Variations of the static air pressure in the external ear canal ranging from 0 to +/- 400 mmH2O induce an inward-outward movement of the malleus. In the regular middle-ear, the direction of this movement is changed within the ossicular chain into a predominantly upward-downward direction of the lenticular process, due to a gliding function of the incudo-malleal (IM) joint. This results in a gliding movement of the surfaces of the incudostapedial joint (IS). In this way, the stapes and the inner-ear are decoupled from the excessive displacements of the drum membrane and malleus. This change in the mode of motion explains many former results of ossicle vibration, aroused by unphysiologically high sound pressures, like v. Békésy's description of the tilting footplate. This mode of motion, however, changes completely if the gliding function of the IM-joint is cancelled by experimental ankylosis. In that case, the predominant direction of movement at the incus and stapes is inward and outward, too. This mode of motion has been the generally accepted concept of the ossicle-chain mechanics up to now. This isodirectional motion also occurs with progressive exsiccation of the temporal bone preparations, explicable with drying and shrinking of the capsular ligament of the IM-joint. It is conceivable, therefore, that our concepts of the mechanics of the ossicle-chain were partly based on experiments with insufficiently moistened temporal bone preparations, as the methodological problem of the exsiccation became known only during recent decades. In further experiments with static air pressure, the mechanics of the reconstructed ossicle-chain, i.e. tympanoplasty and stapedial prostheses, were studied. In the columella-like chain reconstruction, the displacement of the stapes equals the values measured with the ankylosed IM-joint. This displacement is limited by the strength of the annular ligament, whose function, however, is eliminated in the case of stapedial prostheses. Now the displacement is limited by the friction of the piston at the perforation in the footplate.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMedDate not supplied

Three-dimensional graphic reconstruction of the tympanic bulla of the rat with special reference to the middle ear muscles.

On the basis of functional questions, graphic three-dimensional reconstructions of the tympanic bulla of the rat were made to gain insight into the spatial organisation of the contents of the bulla and especially of the tympanic membrane--ossicular chain--middle ear muscle complex. For this purpose drawings of microscopical sections of complete bullae were fed into the computer to make three-dimensional graphic reconstructions with hidden line removal. From these reconstructions plastic representations were made by the medical artist. The topographical anatomy of the tympanic bulla is discussed in detail and compared to the anatomy of the middle ear in man. It is postulated that, despite differences in spatial organisation of the middle ear of the rat compared to that of man, the middle ear muscles influence the ossicular chain in a comparable way. On the basis of the topographical anatomy it is feasible that the muscles in the rat act synergistically in increasing the stiffness of the ossicular chain.

Animals↗
PubMed1980

The acoustic reflex pattern studied by the averaging technique.

The acoustic reflex threshold and its pattern in response to stimuli of different intensities, were investigated by means of the signal-averaging technique in 20 normal, 20 sensorineural-impaired and 10 successfully stapedectomized ears. Trains of tone bursts between 110 and 0 dB HL were used. The frequencies tested were 500, 1 000, 2 000 and 4 000 Hz. In all normal subjects, the pattern of the acoustic reflex for stimuli between 110 and 100 dB HL was biphasic with an initial positive plateau followed by a longer negative one. For stimuli below 80 dB HL, the pattern of the reflex was monophasic with a single positive peak. In the sensorineural-impaired ears, the same double pattern of the waveform was obtained. In the stapedectomized ears, no compliance changes were observed for any sound stimuli. By the averaging technique, the difference between the acoustic reflex threshold and the auditory threshold was found to be between 7.5 and 32.5 dB, in normal and sensorineural-impaired ears.

Acoustic Impedance Tests↗
PubMed2003

[New aspects of the mechanics of the auditory tube].

The aim of the present article is to describe the mechanical components of the auditory tube and the role of these components in auditory tube function. Particular attention will be given to those aspects which have not been sufficiently dealt with in the past, such as the role of the isthmus region, the function of the lateral mucosal folds, the significance of the of the surfactant proteins and the pathophysiology of the patulous auditory tube. Special attention is given to the tensor veli palatini muscle and its physiology. Because of its isometric contraction, the function of this muscle depends on so-called hypomochlia changing the direction of its force. In the context of this article, the three hypomochlia involved are the pterygoid hamulus, Ostmann's fatty tissue and the medial pterygoid muscle. The so-called "Eppendorf-maneuver" is depicted for the first time.

Biomechanical Phenomena↗
PubMed1992

[The mechanics and function of the middle ear. Part 1: The ossicular chain and middle ear muscles].

The revelation of a sophisticated micro-mechanism within the ossicular chain--the gliding of the joints results in a characteristic change of the ossicular movement--extended our conception of the function of the ossicular chain. Contrary to our former ideas of the transmission of sound during hearing, the ossicles do not rotate around an axis, which runs through the center of mass of the malleus and anvil. The imaginary rotational axis is located outside the ossicles, resulting in a more piston-like vibration of the complete chain. The ossicular joints are rigid. This acoustic function of the ossicular chain must rigorously be separated from its behaviour at changes of static, ambient air pressure. The middle ear, working as a sensitive pressure receptor also reacts to these pressure changes with comparatively huge displacements of the drum membrane (visible in pneumatic otoscopy). Only now the malleus rotates around its axial ligaments. These movements cause a gliding motion in the malleus-incus joint, which results in a predominant up- and downward movement of the anvil; the incudo-stapedial joint glides, too, and the stapes (and the inner ear) are decoupled. This micro-mechanism explains several anatomical features of the middle ear construction, as there are the vertical alignment of the incudo-stapedial joint, the suspension of the anvil, the design of the malleus joint, etc. It also accounts for the peculiar anatomical arrangement of the middle ear muscles. Their function can be interpreted as preserving the intact cartilage of the ossicular joints.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗