Tensor tympani muscle

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Tensor tympani muscle
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Details
Origin Auditory tube
Insertion Handle of the malleus
Artery Superior tympanic artery
Nerve Medial pterygoid nerve from the mandibular nerve (V3)
Actions Tensing the tympanic membrane
Identifiers
Latin musculus tensor tympani
MeSH D013719
TA98 A15.3.02.061
TA2 2102
FMA 49028
Anatomical terms of muscle

The tensor tympani is a muscle within the middle ear, located in the bony canal above the bony part of the auditory tube, and connects to the malleus bone. Its role is to dampen loud sounds, such as those produced from chewing, shouting, or thunder. Because its reaction time is not fast enough, the muscle cannot protect against hearing damage caused by sudden loud sounds, like explosions or gunshots, however some individuals have voluntary control over the muscle, and may tense it pre-emptively.

Contents

Structure

Insertion of the tensor tympani muscle onto the malleus. . AA' (two fibrous collagenic layers); B epidermis; C mucous membrane; D head of malleus; E incus; F stapes; G tensor tympani; H lateral process of malleus; I Manubrium of malleus; J stapedius muscle. Tensor tympani-muscle.jpg
Insertion of the tensor tympani muscle onto the malleus. . AA’ (two fibrous collagenic layers); B epidermis; C mucous membrane; D head of malleus; E incus; F stapes; G tensor tympani; H lateral process of malleus; I Manubrium of malleus; J stapedius muscle.

The tensor tympani is a muscle that is present in the middle ear. It arises from the cartilaginous part of the auditory tube, and the adjacent great wing of the sphenoid. It then passes through its own canal, and ends in the tympanic cavity as a slim tendon that connects to the handle of the malleus. The tendon makes a sharp bend around the processus cochleariformis, part of the wall of its cavity, before it joins with the malleus. [1]

The tensor tympani receives blood from the middle meningeal artery via the superior tympanic branch. [1] It is one of two muscles in the tympanic cavity, the other being the stapedius. [1]

Nerve supply

The tensor tympani is supplied by the tensor tympani nerve, a branch of the mandibular branch of the trigeminal nerve. [1] [2] As the tensor tympani is supplied by motor fibers of the trigeminal nerve, it does not receive fibers from the trigeminal ganglion, which has sensory fibers only.

Development

The tensor tympani muscle develops from mesodermal tissue in the 1st pharyngeal arch. [3]

Function

The tensor tympani acts to damp 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. It is not to be confused by the acoustic reflex, but can be activated by the startle reflex.

Voluntary control

Contracting muscles produce vibration and sound. [4] 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).

Some individuals can voluntarily produce this rumbling sound by contracting the muscle. According to the National Institute of Health, "voluntary control of the tensor tympani muscle is an extremely rare event", [5] where "rare" seems to refer more to the scarcity of test subjects and/or studies than the percentage of the general population who have voluntary control. The rumbling sound can also be heard when the neck or jaw muscles are highly tensed as when yawning deeply. This phenomenon has been known since (at least) 1884. [6]

Involuntary control (tympanic reflex)

The tympanic reflex helps prevent damage to the inner ear by muffling the transmission of low frequency vibrations from the tympanic membrane to the oval window. The reflex has a response time of 40 milliseconds, not fast enough to protect the ear from sudden loud noises such as an explosion or gunshot.

Examples of the onset and recovery of the acoustic reflex measured with a laser Doppler velocimetry system LDV AR measurement USAARL.png
Examples of the onset and recovery of the acoustic reflex measured with a laser Doppler velocimetry system

Thus, the reflex most likely developed to protect early humans from loud thunder claps which do not happen in a split second. [7] [8]

The reflex works by contracting the muscles of the middle ear, the tensor tympani and the stapedial muscle. However, the stapedial muscle is innervated by the facial nerve while the tensor tympani is innervated by the trigeminal nerve. The tensor tympani pulls the manubrium of the malleus inwards and tightens it while the stapedial muscle pulls the stapes inward. This tightening damps the sound vibration that is allowed to penetrate the cochlea. Withdrawal from drugs such as benzodiazepines had been known to cause tonic tensor tympani syndrome (TTTS) during withdrawal. The tympanic reflex will also activate when loud vibrations are generated by the person themselves. The tensor tympani can often be observed vibrating while shouting at an increased volume, damping the sound somewhat.

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).

The mechanisms behind dysfunction of the tympanic tensor muscle and their consequences are hypothesized. However, in a published study, researchers studied the case of an acoustic shock whose mechanisms suggest dysfunction of the tympanic tensor muscle. This study appears to be the first to provide experimental support suggesting that middle ear muscles (MEM) may behave abnormally after an acoustic shock. It is suggested that abnormal contractions (e.g. tonic contractions) of the tympanic tensor muscle may trigger neurogenic inflammation. Indeed, fibers with substances P and CGRP were found in close proximity. [9] [10]

Additional images

See also

Related Research Articles

<span class="mw-page-title-main">Middle ear</span> Portion of the ear internal to the eardrum, and external to the oval window of the inner ear

The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea.

The ossicles are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sound vibrations sent from the ear drum to the fluid-filled labyrinth (cochlea). The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss. The term "ossicle" literally means "tiny bone". Though the term may refer to any small bone throughout the body, it typically refers to the malleus, incus, and stapes of the middle ear.

<span class="mw-page-title-main">Eardrum</span> Membrane separating the external ear from the middle ear

In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear, and thence to the oval window in the fluid-filled cochlea. The ear thereby converts and amplifies vibration in the air to vibration in cochlear fluid. The malleus bone bridges the gap between the eardrum and the other ossicles.

<span class="mw-page-title-main">Facial nerve</span> Cranial nerve VII, for the face and tasting

The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue. The nerve typically travels from the pons through the facial canal in the temporal bone and exits the skull at the stylomastoid foramen. It arises from the brainstem from an area posterior to the cranial nerve VI and anterior to cranial nerve VIII.

Articles related to anatomy include:

<span class="mw-page-title-main">Trigeminal nerve</span> Cranial nerve responsible for the faces senses and motor functions

In neuroanatomy, the trigeminal nerve (lit. triplet nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name (trigeminal, from Latin tri- 'three' and -geminus 'twin') derives from each of the two nerves (one on each side of the pons) having three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions. Adding to the complexity of this nerve is that autonomic nerve fibers as well as special sensory fibers (taste) are contained within it.

<span class="mw-page-title-main">Glossopharyngeal nerve</span> Cranial nerve IX, for the tongue and pharynx

The glossopharyngeal nerve, also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper medulla, just anterior to the vagus nerve. Being a mixed nerve (sensorimotor), it carries afferent sensory and efferent motor information. The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, whereas the sensory division originates from the cranial neural crest.

<span class="mw-page-title-main">Auditory system</span> Sensory system used for hearing

The auditory system is the sensory system for the sense of hearing. It includes both the sensory organs and the auditory parts of the sensory system.

<span class="mw-page-title-main">Ear</span> Organ of hearing and balance

An ear is the organ that enables hearing and body balance using the vestibular system. In mammals, the ear is usually described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and the ear canal. Since the outer ear is the only visible portion of the ear in most animals, the word "ear" often refers to the external part alone. The middle ear includes the tympanic cavity and the three ossicles. The inner ear sits in the bony labyrinth, and contains structures which are key to several senses: the semicircular canals, which enable balance and eye tracking when moving; the utricle and saccule, which enable balance when stationary; and the cochlea, which enables hearing. The ear canal is cleaned via earwax, which naturally migrates to the auricle. The ears of vertebrates are placed somewhat symmetrically on either side of the head, an arrangement that aids sound localization.

<span class="mw-page-title-main">Acoustic reflex</span> Small muscle contraction in the middle ear in response to loud sound

The acoustic reflex is an involuntary muscle contraction that occurs in the middle ear in response to loud sound stimuli or when the person starts to vocalize.

Hyperacusis is an increased sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly; it often revolves around damage to or dysfunction of the stapes bone, stapedius muscle or tensor tympani (eardrum). It is often categorized into four subtypes: loudness, pain, annoyance, and fear. It can be a highly debilitating hearing disorder.

<span class="mw-page-title-main">Stapedius muscle</span> Muscle in the human ear

The stapedius is the smallest skeletal muscle in the human body. At just over one millimeter in length, its purpose is to stabilize the smallest bone in the body, the stapes or stirrup bone of the middle ear.

<span class="mw-page-title-main">Tympanic cavity</span> Small cavity surrounding the bones of the middle ear

The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound.

<span class="mw-page-title-main">Tensor veli palatini muscle</span> Muscle of the soft palate

The tensor veli palatini muscle is a thin, triangular muscle of the head that tenses the soft palate and opens the Eustachian tube to equalise pressure in the middle ear.

<span class="mw-page-title-main">Pharyngeal arch</span> Embryonic precursor structures in vertebrates

The pharyngeal arches, also known as visceral arches, are transient structures seen in the embryonic development of humans and other vertebrates, that are recognisable precursors for many structures. In fish, the arches support the gills and are known as the branchial arches, or gill arches.

<span class="mw-page-title-main">Infratemporal fossa</span> Cavity that is part of the skull

The infratemporal fossa is an irregularly shaped cavity that is a part of the skull. It is situated below and medial to the zygomatic arch. It is not fully enclosed by bone in all directions. It contains superficial muscles, including the lower part of the temporalis muscle, the lateral pterygoid muscle, and the medial pterygoid muscle. It also contains important blood vessels such as the middle meningeal artery, the pterygoid plexus, and the retromandibular vein, and nerves such as the mandibular nerve (CN V3) and its branches.

Acoustic shock is the set of symptoms a person may experience after hearing an unexpected, loud sound. The loud sound, called an acoustic incident, can be caused by feedback oscillation, fax tones, or signalling tones. Telemarketers and call centre employees are thought to be most at risk.

<span class="mw-page-title-main">Hearing</span> Sensory perception of sound by living organisms

Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory science.

Tonic tensor tympani syndrome is a disease of the tensor tympani muscle, described by Klochoff et al. in 1971. It involves a decrease in the contraction threshold of the tensor tympani. This hypercontraction leads to chronic ear pain, in particular in the case of hyperacusis and acoustic shock.

References

PD-icon.svgThis article incorporates text in the public domain from page 1046 of the 20th edition of Gray's Anatomy (1918)

  1. 1 2 3 4 Standring, Susan, ed. (2016). "Middle ear: Tensor tympani". Gray's anatomy : the anatomical basis of clinical practice (41st ed.). Philadelphia. p. 637. ISBN   9780702052309. OCLC   920806541.{{cite book}}: CS1 maint: location missing publisher (link)
  2. ↑ Vielsmeier, Veronika; Schlee, Winfried; Langguth, Berthold; Kreuzer, Peter M.; Hintschich, Constantin; Strohmeyer, Lea; Simoes, Jorge; Biesinger, Eberhard (2021). "17 - Lidocaine injections to the otic ganglion for the treatment of tinnitus—A pilot study". Progress in Brain Research. Vol. 260. Elsevier. pp. 355–366. doi:10.1016/bs.pbr.2020.08.006. ISBN   978-0-12-821586-9. ISSN   0079-6123. PMID   33637227. S2CID   226491220.
  3. ↑ Moore, Keith (2003). The Developing Human: Clinically Oriented Embryology (7th ed.). Philadelphia, Pennsylvania: Saunders. pp. 204–208. ISBN   0-7216-9412-8.
  4. ↑ Barry DT (1992). "Vibrations and sounds from evoked muscle twitches". Electromyography and Clinical Neurophysiology. 32 (1–2): 35–40. PMID   1541245.
  5. ↑ Angeli, R. D.; Lise, M.; Tabajara, C. C.; Maffacioli, T. B. (2013). "Voluntary contraction of the tensor tympani muscle and its audiometric effects". The Journal of Laryngology and Otology. 127 (12): 1235–1237. doi:10.1017/S0022215113003149. PMID   24289817. S2CID   26997609.
  6. ↑ cf : Tillaux Paul Jules, Traité d’Anatomie topographique avec applications à la chirurgie, Paris Asselin et Houzeau publishers (4°ed. 1884, p. 125 )
  7. ↑ Saladin, Kenneth (2012). Anatomy and Physiology: The Unity of Form and Function (6th ed.). New York: McGraw-Hill. p. 601. ISBN   978-0-07-337825-1.
  8. ↑ Jones, Heath G.; Nathaniel T. Greene; William A. Ahroon (2018). "Human middle-ear muscles contract in anticipation of acoustic impulses: Implications for hearing risk assessments". Hearing Research. 378: 53–62. doi:10.1016/j.heares.2018.11.006. PMID   30538053. S2CID   54445405.
  9. ↑ Londero A, Charpentier N, Ponsot D, Fournier P, Pezard L and Noreña AJ (2017) A Case of Acoustic Shock with Post-trauma Trigeminal-Autonomic Activation. Front. Neurol. 8:420. doi: 10.3389/fneur.2017.00420
  10. ↑ Yamazaki M, Sato I. Distribution of substance P and the calcitonin gene-related peptide in the human tensor tympani muscle. European Archives of Oto-Rhino-Laryngology. 2014;271(5):905-911. doi:10.1007/s00405-013-2469-1.
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