Tensor tympani muscle

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Tensor tympani muscle
The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above.
The medial wall and part of the posterior and anterior walls of the right tympanic cavity, lateral view. (Label for "Tensor tympani muscle" is at right, second from bottom.)
Details
OriginAuditory tube
InsertionHandle of the malleus
ArterySuperior tympanic artery
NerveMedial pterygoid nerve from the mandibular nerve (V3)
ActionsTensing the tympanic membrane
Identifiers
LatinMusculus tensor tympani
MeSHD013719
TA98A15.3.02.061
TA22102
FMA49028
Anatomical terms of muscle

The tensor tympani is a muscle within the ear. It is contained in the bony canal above the osseous portion of the auditory tube. Its role is to dampen sounds, such as those produced from chewing.

Structure

Insertion of the tensor tympani muscle onto the malleus. . AA’ ( two fibrous collagenic layers); B épidermis; C mucous membrane; D head of malleus; E uncus; F stapes; G tensor tympani; H lateral process of malleus; I Manubrium of malleus; J stapes muscle.

The tensor tympani 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, known as the processus cochleariformis, and is inserted into the handle of the malleus, near its root. [1] : 862 

The tensor tympani is the larger of the two muscles of the tympanic cavity, the other being the stapedius.

Innervation

Innervation of the tensor tympani is from the tensor tympani nerve, a branch of the mandibular division of the trigeminal nerve. [1]: 863  As the tensor tympani is innervated by motor fibres of the trigeminal nerve, it does not receive fibres from the trigeminal ganglion, which has sensory fibres only.

Development

The tensor tympani muscle develops from mesodermal tissue in the 1st pharyngeal arch.[2]

Function

The tensor tympani acts to dampen the noise produced by chewing. When tensed, the muscle pulls the malleus medially, tensing the tympanic membrane and damping vibration in the ear ossicles and thereby reducing the perceived amplitude of sounds. [1]: 863 

Voluntary control

Contracting muscles produce vibration and sound.[3] Slow twitch fibers produce 10 to 30 contractions per second (equivalent to 10 to 30 Hz sound frequency). Fast twitch fibers produce 30 to 70 contractions per second (equivalent to 30 to 70 Hz sound frequency).[4] The vibration can be witnessed and felt by highly tensing one's muscles, as when making a firm fist. The sound can be heard by pressing a highly tensed muscle against the ear, again a firm fist is a good example. The sound is usually described as a rumbling sound. Many individuals can voluntarily produce this rumbling sound by contracting the tensor tympani muscle of the middle ear. The rumbling sound can also be heard when the neck or jaw muscles are highly tensed as when yawning deeply. This phenomenon is known since (at least) 1884 (cf : Tillaux Paul Jules, Traité d’Anatomie topographique avec applications à la chirurgie, Paris Asselin et Houzeau publishers (4°ed. 1884, p. 125 )).

Clinical significance

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).[5][6]

Additional images

  • Base of skull. Inferior surface.
    Base of skull. Inferior surface.
  • External and middle ear, opened from the front. Right side.
    External and middle ear, opened from the front. Right side.
  • View of the inner wall of the tympanum (enlarged.)
    View of the inner wall of the tympanum (enlarged.)
  • Auditory tube, laid open by a cut in its long axis.
    Auditory tube, laid open by a cut in its long axis.

References

Public domain This article incorporates text in the public domain from page 1046 of the 20th edition of Gray's Anatomy (1918)

  1. ^ a b c Drake, Richard L. (2005). Gray's anatomy for students (Pbk. ed.). Philadelphia: Elsevier/Churchill Livingstone. ISBN 978-0-443-06612-2. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  2. ^ Moore, Keith (2003). The Developing Human: Clinically Oriented Embryology 7th Ed. Philadelphia, Pennsylvania: Saunders. pp. 204–208. ISBN 0-7216-9412-8.
  3. ^ U.S. National Library of Medicine, National Institutes of Health, Barry DT., Vibrations and sounds from evoked muscle twitches., Electromyogr Clin Neurophysiol. 1992 Jan-Feb;32(1-2):35-40.
  4. ^ September 2009 - Welcome to racewalkingnewzealand.org, PROGRAM FITNESS NEWSLETTER September 2009 by Gary Little
  5. ^ http://www.tinnitusvic.asn.au/tinnitus-hyperacusis.htm
  6. ^ http://www.tinnitus.org/home/frame/Tensor%20tympani%20syndrome_Klochoff.pdf

See also

This article uses anatomical terminology.

External links

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