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The tensor tympani, the larger of the two muscles of the tympanic cavity, is contained in the bony canal above the osseous portion of the auditory tube, from which it is separated by the septum canalis musculotubarii.
Origin and insertion
It arises from the cartilaginous portion of the auditory tube and the adjoining part of the great wing of the sphenoid, as well as from the osseous canal in which it is contained.
Passing backward through the canal, it ends in a slender tendon which enters the tympanic cavity, makes a sharp bend around the extremity of the septum, and is inserted into the manubrium of the malleus, near its root.
Function
When tensed, the action of the muscle is to pull the malleus medially, tensing the tympanic membrane, damping vibration in the ear ossicles and thereby reducing the amplitude of sounds. This muscle is contracted primarily to dampen the noise produced by chewing. (Compare to the more general dampening function of the stapedius muscle.)
In many people with hyperacusis, an increased activity develops in the tensor tympani muscle in the middle ear as part of the startle response to some sounds. This lowered reflex threshold for tensor tympani contraction is activated by the perception/anticipation of loud sound, and is called tonic tensor tympani syndrome (TTTS). In some people with hyperacusis, the tensor tympani muscle can contract just by thinking about a loud sound. Following exposure to intolerable sounds, this contraction of the tensor tympani muscle tightens the ear drum, which can lead to the symptoms of ear pain/a fluttering sensation/a sensation of fullness in the ear (in the absence of any middle or inner ear pathology)[1][2]. A small percentage of the population can actually voluntarily contract this muscle, inducing a noticeable and (until explained) odd 'rumbling' sound to occur [3].
Innervation
Innervation of the muscle is from branches of the mandibular division of the trigeminal nerve (V), by way of the Trigeminal ganglion.
Additional images
Base of skull. Inferior surface.
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External and middle ear, opened from the front. Right side.
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View of the inner wall of the tympanum (enlarged.)
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Auditory tube, laid open by a cut in its long axis.
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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
See also
External links
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