Dominic Stone
The human ear is an extremely complex organ, and its intricate workings are not yet fully understood. While the ear is not all muscle, it does contain two muscles in the middle ear, known as the tensor tympani and the stapedius. These muscles are thought to play a role in protecting the ear from loud noises, with some individuals able to voluntarily contract the tensor tympani muscle to produce a rumbling sound. This phenomenon has been likened to putting your hands over your ears or hearing a roar. However, the tensor tympani's reaction time is not fast enough to protect against sudden loud noises like explosions or gunshots. The stapedius muscle is the main protector against external auditory stimuli, and its contraction increases middle ear stiffness, reducing the transmission of low-frequency sounds.
| Characteristics | Values |
|---|---|
| Number of muscles in the ear | 2 |
| Names of the muscles | Tensor Tympani, Stapedius |
| Location of the muscles | Middle ear |
| Function of the muscles | Protect the ear from loud noises |
| Tensor Tympani muscle origin | Auditory tube (Eustachian tube) |
| Tensor Tympani insertion point | Manubrium of the eardrum |
| Stapedius muscle origin | N/A |
| Stapedius insertion point | Close wall of the middle ear |
| Tensor Tympani nerve | Trigeminal nerve |
| Stapedius nerve | Facial nerve |
| Tensor Tympani blood supply | Middle meningeal artery |
| Stapedius blood supply | N/A |
| Tensor Tympani contraction sound | Roaring or rumbling |
| Stapedius contraction sound | High-pitched "tick" |
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What You'll Learn
- The tensor tympani and stapedius are the two muscles in the middle ear
- The tensor tympani muscle is innervated by the trigeminal nerve
- The stapedius muscle is innervated by the facial nerve
- The tensor tympani muscle can be voluntarily contracted, producing a rumbling sound
- The stapedius muscle may be overactive, causing a high-pitched tick sound
The tensor tympani and stapedius are the two muscles in the middle ear
The human ear does contain muscles. Specifically, the middle ear contains two muscles: the tensor tympani and the stapedius. These muscles function to protect the ear from loud noises.
The tensor tympani muscle is a tiny but long muscle that is present in the middle ear. It arises from the cartilaginous part of the auditory tube (or Eustachian tube) and the adjacent great wing of the sphenoid bone. 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, one of the three auditory ossicles. The tensor tympani is innervated by the trigeminal nerve and receives blood from the middle meningeal artery via the superior tympanic branch. When tensed, the tensor tympani pulls the malleus medially, tensing the tympanic membrane and reducing the amplitude of sound transmitted to the inner ear. This is known as the tympanic reflex, an evolutionary adaptation to protect the inner ear from excessively loud natural noises, such as thunder.
The stapedius muscle is much smaller than the tensor tympani and runs from the stapes to the wall of the middle ear. It is innervated by the tympanic branch of the 7th nerve. The stapedius contracts the stapes of the oval window, thereby decreasing the propagation of high-intensity sound. Both the tensor tympani and the stapedius muscles are involved in the acoustic reflex, which protects inner ear cells from damage by involuntarily contracting in response to high-intensity sounds.
Abnormal contractions of the tensor tympani muscle, such as tonic contractions, may trigger neurogenic inflammation and are associated with tensor tympani syndrome (TTS) or middle ear myoclonus. TTS is characterised by symptoms such as ear pain, a fluttering sensation, or a sensation of fullness in the ear. Similarly, abnormal contractions of the stapedius muscle are associated with stapedius myoclonus, which can cause a high-pitched "tick" sound.
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The tensor tympani muscle is innervated by the trigeminal nerve
The ear has two muscles within the middle ear that function to protect it from loud noises: the tensor tympani and the stapedius. The tensor tympani muscle is a tiny but long paired muscle of the middle ear. It is 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.
The tensor tympani muscle develops from mesodermal tissue in the first pharyngeal arch. It receives its innervation via a motor branch of the trigeminal nerve. The motor part of the trigeminal nerve innervates several muscles, including the masseter, temporalis, lateral and medial pterygoids, tensor tympani, tensor veli palatini, mylohyoid, and the anterior belly of the digastric muscle.
The trigeminal nerve has three main branches of sensory fibers: the maxillary nerve, the mandibular nerve, and the sensory fibers from the trigeminal ganglion. The maxillary nerve is sensory to the upper lip mucosa, maxilla, upper teeth, cheeks, palate, and maxillary sinus. The mandibular nerve is sensory to the anterior two-thirds of the tongue, mandible, lower teeth, lower lip, part of the cheek, and part of the external ear. The trigeminal ganglion has sensory fibers only and does not supply the tensor tympani muscle.
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The stapedius muscle is innervated by the facial nerve
The ear has two muscles, the Tensor Tympani and the Stapedius, which are located in the middle ear. The Stapedius muscle is the smallest skeletal muscle in the human body, measuring just over one millimeter in length. Its function is to stabilize the smallest bone in the body, the stapes (or stirrup bone) of the middle ear. The stapedius muscle emerges from a small opening in the apex of the pyramidal eminence (a hollow, cone-shaped prominence in the posterior wall of the tympanic cavity) and inserts into the neck of the stapes.
The stapedius muscle plays an important role in sound transmission and protection. When incoming sound stimulates the receptor cells in the inner ear, signals are sent to the cochlear nucleus in the brainstem. From there, efferent signals trigger the contraction of the stapedius muscle, resulting in the posterior rotation of the stapes. This action closes the vestibular window, attenuating further vibrations passed to the cochlea and protecting the hearing apparatus from loud sounds.
The stapedius muscle's contraction also increases middle ear stiffness and reduces the transmission of low-frequency sounds. This is particularly relevant for subterranean mammals, which have disproportionately lost the stapedius muscle. The loss of this muscle is suggested to be associated with improved low-frequency hearing in these mammals.
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The tensor tympani muscle can be voluntarily contracted, producing a rumbling sound
The tensor tympani is a muscle located in the middle ear, above the auditory tube. It is one of two muscles in the tympanic cavity, the other being the stapedius muscle. The tensor tympani muscle is connected to the malleus bone. This muscle plays a crucial role in various auditory processes, including regulating the movement of the eustachian tube and stiffening the tympanic membrane to dampen sound transmission in response to high-intensity sounds.
The tensor tympani muscle can be voluntarily contracted by some people, which produces a low, rumbling sound in their ears. This is an extremely rare phenomenon, according to the National Institute of Health. When the tensor tympani muscle is voluntarily contracted, it pulls the malleus medially, tensing the tympanic membrane and reducing the perceived amplitude of sounds. This results in a rumbling sound that can be heard by the individual.
In some cases, individuals with hyperacusis may experience tonic tensor tympani syndrome (TTTS) or tensor tympani myoclonus, a rare condition characterized by involuntary contractions of the tensor tympani muscle. This can lead to symptoms such as ear pain, a fluttering sensation, or a feeling of fullness in the ear. The tensor tympani muscle can also be activated by the startle reflex or the perception of loud sounds, causing a tightening of the eardrum.
The ability to voluntarily contract the tensor tympani muscle is an intriguing aspect of ear anatomy. While it is a rare ability, it showcases the complexity of the ear and its muscles. For those who can contract this muscle voluntarily, it offers a unique sensory experience of hearing the sound of their own muscle contractions.
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The stapedius muscle may be overactive, causing a high-pitched tick sound
The ear has two muscles in the middle ear: the tensor tympani and the stapedius. The tensor tympani muscle originates from the auditory tube (also known as the Eustachian tube) and inserts onto the manubrium of the eardrum. The tensor tympani is innervated by the trigeminal nerve, specifically the mandibular division (V) through the trigeminal ganglion. The stapedius muscle, on the other hand, is innervated by the facial nerve.
The tensor tympani and stapedius muscles are protective reflexes that reduce the amount of sound that reaches the inner ear. They are similar to the blink reflex and can be triggered by loud noises. When the tensor tympani muscle is tensed, it pulls the malleus medially, tightening the tympanic membrane and reducing the perceived amplitude of sounds. This tightening dampens sound vibrations that penetrate the cochlea.
The stapedius muscle typically contracts the stapes of the oval window to decrease the propagation of high-intensity sound. It is more sensitive to sound than the tensor tympani and is thought to be the dominant sound-generated reflex in humans. The stapedius may also contract during internal vocalization to reduce self-stimulation.
In some cases, the stapedius muscle may be overactive, leading to a condition known as stapedius myoclonus. This can cause a high-pitched "tick" sound, which may be indicative of tinnitus. Stapedius myoclonus can be challenging to diagnose, and surgery to cut the muscle is typically a last resort.
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Frequently asked questions
Yes, the human ear has two muscles in the middle ear, the tensor tympani and the stapedius.
The tensor tympani and the stapedius work together to protect the ear from loud noises. The tensor tympani is not fast enough to protect against sudden loud noises like explosions or gunshots. The stapedius is the main muscle involved in protecting the ear from external auditory stimuli.
When the tensor tympani muscle is contracted, it pulls the malleus medially, tightening the tympanic membrane and reducing the perceived amplitude of sounds. Some people can voluntarily contract this muscle and hear a low, rumbling noise in their ears.
