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Humans have vestigial ear muscles that are considered non-functional, though they may still be large enough to be easily identified. These muscles are the three extrinsic auricular muscles—the posterior, superior, and anterior auricular muscles—and the six intrinsic muscles—the helicis major and minor, tragicus, anti-tragicus, transverse, and oblique muscles. In other mammals, the auricular muscles can adjust the direction of the pinna, but in humans, they have little to no effect. However, some people are able to voluntarily move their ears in various directions, and it may be possible for others to gain such movement through repeated trials.
| Characteristics | Values |
|---|---|
| Number of extrinsic ear muscles | 3 |
| Extrinsic ear muscles | Superior auricular muscle (SAM), posterior auricular muscle (PAM), and anterior auricular muscle (AAM) |
| Number of intrinsic ear muscles | 6 |
| Intrinsic ear muscles | Helicis major (HMJM) and helicis minor (HMNM) muscles, tragicus muscle (TR), anti-tragicus muscle (ATR), transverse auricular muscle (TAM), and oblique muscle (OAM) |
| Vestigial muscles | Yes |
| Function of vestigial muscles | Activate when listening closely to something |
| Muscle that raises the ears | One of the vestigial muscles |
| Muscle that pulls the ear back | Another vestigial muscle |
| Muscle that controls the pinna | Palmaris longus |
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What You'll Learn
- Humans have vestigial ear muscles that activate when listening intently
- The human ear has three extrinsic and six intrinsic muscles
- Intrinsic ear muscles have no function in humans
- Extrinsic ear muscles pull the ear upward, forward, and backward
- Vestigial ear muscles may be used to monitor and treat neurological disorders
Humans have vestigial ear muscles that activate when listening intently
Humans have vestigial ear muscles that are thought to activate when listening intently. These muscles, which can be found in the outer ear, are called the intrinsic and extrinsic muscles. In other mammals, these muscles can adjust the direction of the pinna, or the external part of the ear, to improve hearing by capturing sound more effectively. However, in humans, these muscles have little to no effect on the movement of the pinna.
The three extrinsic auricular muscles are the posterior, superior, and anterior auricular muscles. The superior auricular muscle is the largest of the three extrinsic muscles and it pulls the ear upward. The anterior auricular muscle is the smallest of the three and its fibres are slight and easily overlooked. The posterior auricular muscle pulls the ear backward.
There are also six intrinsic auricular muscles: the helicis major and minor, tragicus, anti-tragicus, transverse auricular, and oblique muscles. These muscles have been considered vestigial in humans, though they may play a role in shaping the ear during development in the womb.
A study published in the journal Frontiers in Neuroscience found that when humans listen hard to a sound, some of these muscles become activated. The researchers asked 20 adults without hearing problems to listen to an audiobook while a podcast played at the same time, creating three different scenarios of varying difficulty. They found that as the listening challenge grew more difficult, the superior auricular muscles, which lift the ear upward and outward, became more active. They also found that the posterior auricular muscles, which pull the ear backward, were more active when sounds came from behind the participant.
These findings suggest that vestigial ear muscles in humans may still be active and could potentially be useful for hearing aid technology. For example, a hearing aid could monitor activity in these muscles to adjust the amplification accordingly. Further research is needed to better understand the functionality of these muscles and their potential applications.
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The human ear has three extrinsic and six intrinsic muscles
The extrinsic muscles are responsible for positioning the ear in place. They pull the ear upward, forward, and backward. The intrinsic muscles, on the other hand, play a role in the positioning and formation of the folds of the cartilaginous auricle by connecting the opposite margins of the fissures. Thus, the intrinsic muscles contribute to the overall topography of the human ear.
These muscles have been considered vestigial in humans, meaning they are non-functional structures that have lost their biological function through evolution. However, it has been suggested that they may exert forces on the cartilage and affect the shaping of the ear during development in the womb. In some rare cases, individuals can move their ears by voluntarily contracting these muscles. Additionally, the neural connections of the auricular muscles with the brainstem and other deep brain structures are intact, making them easily accessible for wearable neuroprosthetics and therapeutic or diagnostic devices.
The human ear muscles are supplied by the facial nerve, which also provides sensation to the skin of the ear and the external ear cavity. The great auricular nerve, auricular nerve, auriculotemporal nerve, and lesser and greater occipital nerves of the cervical plexus also supply sensation to parts of the outer ear and the surrounding skin.
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Intrinsic ear muscles have no function in humans
The human ear has two sets of muscles: the intrinsic and extrinsic muscles. The intrinsic ear muscles are the helicis major and minor, tragicus, anti-tragicus, transverse, and oblique muscles. These muscles are vestigial in humans, meaning they have lost their biological function through evolution.
While the intrinsic ear muscles serve no function in humans, they are still large enough to be easily identified. These muscles are considered vestigial, meaning that while they have lost their original function, the structure has been retained. In some other mammals, these muscles can adjust the direction of the pinna, or outer ear. In humans, however, these muscles have little to no effect on the movement of the pinna. This is compensated for by the ability to turn the head on a horizontal plane, a function not common to most monkeys.
The extrinsic auricular muscles, on the other hand, are the posterior, superior, and anterior auricular muscles. These muscles are responsible for pulling the ear upward, forward, and backward, respectively. The superior and anterior auricular muscles are fan-shaped and originate in the epicranial aponeurosis (galea aponeurotica). The superior auricular muscle is the largest of the three extrinsic muscles, while the anterior auricular muscle is the smallest and its fibres are slight and easily overlooked.
Despite having no function in humans, the intrinsic ear muscles have intact neural connections with the brainstem and other deep brain structures. This makes them easily accessible for wearable neuroprosthetics and therapeutic and diagnostic devices. These devices can monitor and alleviate the symptoms of various health conditions, including neurological disorders, brainstem injuries, emotional states, and auditory functions. Additionally, the intrinsic ear muscles contribute to the overall topography of the human ear by playing a role in the positioning and formation of the folds of the cartilaginous auricle.
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Extrinsic ear muscles pull the ear upward, forward, and backward
The human ear is divided into three parts: the outer ear, the middle ear, and the inner ear. The outer ear, or external ear, is the only visible part of the ear and consists of the auricle (also known as the pinna) and the ear canal. The auricle is made of elastic cartilage and is connected to the surrounding parts by ligaments and muscles. The ear canal, also known as the external acoustic meatus, is a simple tube that runs from the auricle to the middle ear.
The outer ear houses both extrinsic and intrinsic auricular muscles. There are three extrinsic auricular muscles: the posterior auricular muscle (PAM), superior auricular muscle (SAM), and anterior auricular muscle (AAM). These muscles are located around the auricula or outer ear. The superior auricular muscle is the largest of the three, followed by the posterior and the anterior. The extrinsic ear muscles pull the ear upward, forward, and backward. The auricularis anterior draws the auricula forward and upward, the auricularis superior slightly raises it, and the auricularis posterior draws it backward.
The intrinsic ear muscles, on the other hand, serve no role in humans. There are six intrinsic muscles: the helicis major and minor, tragicus, antitragicus, transverse, and oblique muscles. These muscles are considered vestigial in humans, meaning they are non-functional structures. However, it has been suggested that they may affect the shaping of the ear during development in the womb.
The auricle of the outer ear can be pulled backward and upward during an otoscopic examination to allow for proper angling of the otoscope tip in the external auditory canal. This movement is facilitated by the extrinsic ear muscles. Additionally, research suggests that the postauricular reflex, a vestigial muscle response, causes the pinna to be pulled upward and backward in response to sudden, surprising sounds. This reflex may be part of an ancient system for monitoring sounds that are out of sight.
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Vestigial ear muscles may be used to monitor and treat neurological disorders
Human ear muscles are considered vestigial, meaning they are evolutionary remnants that once had a purpose but no longer do. These vestigial muscles, including the auricularis posterior muscle and transversus auriculae, are small and weak and do not move the ears. However, they may still exhibit some reflexive movements, such as when we strain to hear a sound.
While these vestigial ear muscles may seem useless, researchers have proposed several potential applications for them in monitoring and treating neurological disorders. Firstly, these muscles may be used to develop better hearing aids. By sensing the electrical activity in the ear muscles, hearing aids could amplify the sounds a person is trying to focus on while minimizing other sounds. This technology could be especially useful for individuals with hearing loss, who often rely on hearing aids or cochlear implants to compensate for their impaired hearing.
Additionally, the neural networks of the auricular muscles can be utilized for wearable neuroprosthetics and biomedical devices. These devices can monitor and treat various conditions, including neurological disorders, brainstem injuries, emotional states, and auditory functions. The intact neural connections between the auricular muscles and the brainstem provide an accessible pathway for these therapeutic and diagnostic tools.
Furthermore, vestigial ear muscles can be used as a tool to study emotions. Researchers have found that the auricularis posterior muscle activates in response to positive emotions, although the reason for this is not yet fully understood. This muscle reflex provides psychologists with an objective way to measure emotion, contributing to our understanding of emotional states and their impact on human behaviour.
In conclusion, while the vestigial ear muscles in humans may no longer serve their original purpose of moving the ears, they have the potential to be repurposed for various applications in medicine and psychology. By leveraging the accessibility of these muscles and their associated neural networks, researchers can develop innovative technologies to monitor and treat a range of conditions, including neurological disorders and hearing impairments. Further research and experimentation are needed to fully unlock the potential of these vestigial ear muscles and their impact on our understanding of human biology and healthcare.
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Frequently asked questions
The mammalian external ear houses extrinsic and intrinsic auricular muscles. The extrinsic muscles are the posterior auricular muscle (PAM), superior auricular muscle (SAM), and anterior auricular muscle (AAM). The intrinsic muscles are the helicis major (HMJM) and minor (HMNM) muscles, tragicus muscle (TR), anti-tragicus muscle (ATR), transverse auricular muscle (TAM), and oblique muscle (OAM).
Human ear muscles are homologous. Humans have vestigial muscles that activate when listening closely to something, even though people lost the ability to really move their ears about 25 million years ago.
In many mammals, ear movements produced by the auricular muscles play a role in sound localization and the expression of emotion, but in humans, the muscles are considered nonfunctional.
