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The smallest muscle in the human body is the Stapedius muscle, which is located in the middle ear. It is responsible for stabilising the smallest bone in the human body, the stapes, which is just over one millimetre long. The Stapedius muscle is also known as the littlest skeletal muscle in the human body. It has a length of between 9 and 11 mm and a tendon length of 2 mm.
| Characteristics | Values |
|---|---|
| Name | Stapedius |
| Type | Skeletal muscle |
| Length | Approximately 1 mm |
| Shape | Sickle |
| Breadth | 2-3 mm |
| Function | Stabilizes the stapes, the smallest bone in the body |
| Role | Protects against hazardous levels of noise and improves speech perception |
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What You'll Learn
The stapedius is the smallest skeletal muscle in the human body
The stapedius muscle is widely recognised as the smallest skeletal muscle in the human body. It measures approximately 6 millimetres in length, although some sources state that it is just over 1 millimetre long, while others report lengths varying between 9 and 11 millimetres. Despite its diminutive size, the stapedius muscle plays a crucial role in the human body, particularly in sound transmission, hearing, and otology.
The stapedius muscle is located in the tympanic cavity of the middle ear. It connects the pyramidal eminence of the petrous part of the temporal bone to the posterior aspect of the neck of the stapes bone. This muscle is innervated by the stapedial branch of the facial nerve, also known as the nerve to stapedius muscle. The stapedius muscle receives its blood supply from the stapedial branch of the posterior auricular artery, a branch of the external carotid artery.
The primary function of the stapedius muscle is to stabilise the stapes bone, which is the smallest bone in the human body. The stapedius muscle helps to control the amplitude of sound waves reaching the inner ear by dampening the vibrations of the stapes bone. It does this by contracting and pulling on the neck of the stapes bone, thereby preventing excessive movement. This protective mechanism is known as the acoustic reflex or the stapedius reflex.
The stapedius muscle contracts involuntarily in response to sounds of a particular volume, especially loud noises. This contraction results in the posterior rotation of the stapes bone, placing its base into the vestibular window and closing it off. As a result, further vibrations transmitted to the cochlea are attenuated, protecting the inner ear from potential damage.
Paralysis of the stapedius muscle can lead to a condition called hyperacusis, where normal sounds are perceived as uncomfortably loud. This occurs because the stapedius muscle can no longer dampen the vibrations transmitted to the cochlea, resulting in heightened sensitivity to sound. Hyperacusis can also be caused by damage to the facial nerve or its branch, the nerve to stapedius, which supplies the stapedius muscle.
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The stapedius muscle is approximately 1 mm in length
The stapedius muscle is the smallest muscle in the human body, measuring approximately 1 mm in length. It is located in the tympanic cavity in the middle ear. It connects the pyramidal eminence of the petrous part of the temporal bone to the posterior aspect of the neck of the stapes. The stapedius muscle is innervated by the stapedial branch of the facial nerve, also known as the nerve to stapedius muscle. These autonomic fibres enable the muscle to be involved in the auditory middle ear reflex, helping to protect the auditory system from damage.
The stapedius muscle has an important role in sound transmission and hearing. It contracts in response to loud sounds, dampening the vibrations of the stapes bone and controlling the amplitude of sound waves from the general external environment to the inner ear. This helps to protect the hearing apparatus when exposed to loud sounds. The stapedius muscle is also involved in improving speech perception in the presence of background noise.
The stapedius muscle has a classical sickle shape, with a tendon that looks like the handle of the sickle. It has a bulky belly with a maximum breadth of 2-3 mm. The muscle is supplied by the stapedial branch of the posterior auricular artery, which branches from the external carotid artery.
The stapedius muscle can be affected by conditions such as hyperacusis, which causes normal sounds to be perceived as very loud. Paralysis of the stapedius muscle can occur when the nerve to the stapedius or the facial nerve itself is damaged. This can result in a failure to attenuate sounds, leading to heightened sensitivity to everyday sounds and potentially complete deafness.
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The stapedius muscle has a classical sickle shape
The stapedius muscle is the smallest skeletal muscle in the human body. It measures between 9 and 11 mm in length, or approximately 6 mm according to another source, with a breadth of 2-3 mm. Despite its small size, it serves a vital function in otology and hearing.
The stapedius muscle is located in the tympanic cavity of the middle ear. It connects the pyramidal eminence of the petrous part of the temporal bone to the posterior aspect of the neck of the stapes. The stapedius muscle is innervated by the stapedial branch of the facial nerve, also known as the nerve to stapedius muscle. This nerve arises from the facial nerve (CN VII).
The main function of the stapedius muscle is to protect the hearing apparatus when exposed to loud sounds. It contracts in response to sounds above a certain volume to stabilise the stapes or stirrup bone of the middle ear. This dampens the vibrations of the stapes and prevents excessive movement, helping to control the amplitude of sound waves entering the inner ear.
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The stapedius muscle stabilises the smallest bone in the body
The stapedius muscle is the smallest muscle in the human body, measuring approximately 6 millimetres in length. It is located in the tympanic cavity in the middle ear. The stapedius muscle is innervated by the stapedial branch of the facial nerve. These autonomic fibres enable the muscle to be involved in the auditory middle ear reflex, which helps to protect the auditory system from damage.
The stapedius muscle emerges from a pinpoint foramen or opening in the apex of the pyramidal eminence, a hollow, cone-shaped prominence in the posterior wall of the tympanic cavity. It then inserts into the neck of the stapes, or stirrup bone of the middle ear. The stapedius dampens the vibrations of the stapes by pulling on the neck of that bone. It prevents excess movement of the stapes, helping to control the amplitude of sound waves from the general external environment to the inner ear.
The stapedius muscle is the effector component of the acoustic middle ear reflex. When incoming sound is loud enough to stimulate the receptor cells in the inner ear, the afferent signal reaches the cochlear nucleus in the brainstem via the vestibulocochlear nerve. From the brainstem, efferent signals are sent to the ipsilateral and contralateral middle ears, triggering the contractions of the stapedius muscles. Their contractions result in the posterior rotation and placement of the base of the stapes into the vestibular window, which closes it and attenuates further vibrations passed to the cochlea. Thus, the main function of the stapedius muscle is to protect the hearing apparatus when exposed to loud sounds.
The stapedius muscle is also important in otology. It has been shown to have a classical sickle shape, with the tendon looking like the handle of the sickle. It has a bulky belly with a maximum breadth of 2-3 millimetres. The stapedius muscle develops from the second brachial arch and is innervated by the branch from the vertical segment of the facial nerve, that is, the nerve to stapedius.
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The stapedius muscle contracts in response to loud sounds
The stapedius muscle is the smallest skeletal muscle in the human body, measuring approximately 6mm in length. It is located in the tympanic cavity in the middle ear, connecting the pyramidal eminence of the petrous part of the temporal bone to the posterior aspect of the neck of the stapes.
The main function of the stapedius muscle is to protect the hearing apparatus when exposed to loud sounds. It does this by dampening the vibrations of the stapes, or stirrup bone of the middle ear, and preventing excessive movement. This helps to control the amplitude of sound waves from the general external environment to the inner ear.
The stapedius muscle is innervated by the stapedial branch of the facial nerve, also known as the nerve to stapedius muscle. Paralysis of the stapedius muscle can result from damage to this nerve or the facial nerve itself, leading to a condition called hyperacusis. Hyperacusis causes everyday sounds to be perceived as very loud due to the failure to attenuate sound from the outside environment.
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Frequently asked questions
The stapedius is the smallest skeletal muscle in the human body, at approximately 1 mm in length.
The stapedius muscle stabilises the stapes, the smallest bone in the body, to keep it from vibrating too violently.
If the stapedius muscle only responds to extremely loud sounds or doesn't contract at all, it may be a sign of hearing loss.
The stapedius muscle originates from the fasciculi of the posterior belly of the digastric muscle, which is inserted in the mastoid groove.
The stapedius muscle has a classical sickle shape with a tendon that looks like the handle of the sickle.
