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The zygomaticus major muscle is a crucial facial muscle that extends diagonally from the zygomatic bone to the angle of the mouth. It is responsible for various facial expressions, including smiling, laughing, and displaying emotions such as disdain, contempt, or smugness. This muscle raises the upper lip, baring the upper teeth, and contributes to the deepening of the nasolabial furrow. Understanding the contraction patterns and visual presentation of the zygomaticus major muscle is essential for enhancing pre-surgical facial assessments and developing new treatment strategies. This muscle is also associated with chewing, speaking, and emotional expression.
| Characteristics | Values |
|---|---|
| Muscle Type | Thin paired facial muscle |
| Origin | Zygomatic bone |
| Insertion | Angle of the mouth |
| Action | Elevates the angle of the mouth |
| Innervation | Zygomatic and buccal branches of facial nerve (CN VII) |
| Arterial Supply | Superior labial artery |
| Functions | Speech, facial expressions, smiling, chewing |
| Contraction Patterns | Isotonic contraction (decreased length, increased width and thickness) |
| Clinical Relevance | Used in reconstructive surgery, pre-surgical facial assessments |
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What You'll Learn
Zygomaticus major is a thin, paired facial muscle
The zygomaticus major muscle originates from the lateral surface of the zygomatic bone, just anterior to the zygomaticotemporal suture, and extends diagonally to the angle of the mouth. It belongs to the buccolabial group of facial muscles, which form the structure and carry out the functions of the cheeks and lips. The buccolabial group includes the levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, levator anguli oris, risorius, depressor labii inferioris, depressor anguli oris, mentalis, orbicularis oris, incisivus superior and inferior, and buccinator muscles.
The zygomaticus major muscle raises the upper lip to bare the upper teeth, deepening and raising the nasolabial furrow. It acts in conjunction with other muscles of facial expression that elevate the lip, curling the upper lip to produce facial expressions such as smiling, disdain, contempt, or smugness. The average muscle can contract with a force of 200g.
The zygomaticus major muscle is innervated by the zygomatic and buccal branches of the facial nerve (CN VII) and is supplied by the superior labial artery, which branches off the facial artery. The facial artery and its accompanying vein run between the buccinator and zygomaticus major muscles.
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It originates from the lateral surface of the zygomatic bone
The zygomaticus major muscle is a crucial facial muscle that plays a key role in smiling and emotional expression. It is responsible for pulling the angle of the mouth superolaterally, contributing to the expression of laughing and smiling. This muscle is also involved in creating various facial expressions and facilitating speech.
Now, let's focus on remembering the detail that "it originates from the lateral surface of the zygomatic bone". The zygomaticus major muscle, as the name suggests, has a close relationship with the zygomatic bone, also known as the cheekbone. The zygomatic bone is an irregularly shaped bone in the skull, situated at the upper and lateral part of the face. It is nearly quadrangular in shape and has three surfaces: the lateral (or facial) surface, the posteromedial surface, and the orbital surface.
The lateral surface of the zygomatic bone, from which the zygomaticus major muscle originates, is smooth and convex. It faces towards the outside of the face. This surface features a small opening called the zygomaticofacial foramen, which serves as a gateway for the transmission of the zygomaticofacial nerve, artery, and vein between the orbit and the face. The zygomaticus major muscle originates from this lateral surface, just anterior to the zygomaticotemporal suture and lateral to the origin of the zygomaticus minor muscle.
To remember this detail, you can visualize the zygomatic bone as a three-dimensional structure with the lateral surface facing outwards. Think of the zygomaticus major muscle arising from this lateral surface, contributing to the movements of the face, particularly the act of smiling and laughing. Additionally, you can create mnemonic devices or visual associations to help you recall this information. For example, you could create a mental image of a person laughing with their cheeks protruding outwards, emphasizing the lateral surface of the zygomatic bone.
By understanding the anatomical structure and function of the zygomaticus major muscle and its relationship with the zygomatic bone, you can improve your ability to recall specific details, such as its origin from the lateral surface of the zygomatic bone. This knowledge will also enhance your understanding of the complex workings of the human body, specifically the role of facial muscles in emotional expression.
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It is responsible for smiling and emotional expression
The zygomaticus major muscle is a crucial facial muscle responsible for smiling and emotional expression. It extends diagonally from the zygomatic bone (cheekbone) to the angle of the mouth, forming part of the structure and function of the cheeks and lips. When the zygomaticus major contracts, it pulls the angle of the mouth superolaterally, producing a smile. In synergy with the risorius muscle, it also deepens the nasolabial furrow, creating expressions such as smiling, disdain, contempt, or smugness.
Research has shown that the zygomaticus major plays a role in distinguishing between genuine and deliberate smiles. Spontaneous smiles, often considered more sincere, tend to be shorter in duration (4-6 seconds), have a slower offset, and are more symmetrical than deliberate smiles. This discrimination can be identified with the help of fEMG recordings of the zygomaticus major, which detect electrical activity underlying muscle movement, even when there is no overt activation.
The zygomaticus major is also associated with positive emotions. Studies have found a linear relationship between the activity of this muscle and the positive valence of stimuli, suggesting that the zygomaticus major and the corrugator supercilii (frowning muscle) could work as proxies for positive and negative emotional responses.
The activation of the zygomaticus major can be measured through facial expression analysis, categorizing muscle movements into discrete action units. This methodology has evolved from manual coding systems to real-time analysis using machine learning software such as Affectiva.
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It pulls the angle of the mouth superolaterally
The zygomaticus major muscle is a crucial facial muscle responsible for smiling and emotional expression. It pulls the angle of the mouth superolaterally, which results in a smile. This muscle works in synergy with the risorius muscle, which is also known as the "smiling muscle". Together, they produce the expression of smiling and contribute to laughing, which is why they are often referred to as the "laughing muscles".
The zygomaticus major muscle originates from the lateral surface of the zygomatic bone, which is also known as the cheekbone. It extends diagonally towards the lips and inserts onto the skin of the upper lip, just medial to the risorius muscle. This attachment point is where the muscle interlaces with other muscles that converge towards the angle of the mouth, forming a dense, mobile, fibromuscular mass called the modiolus.
The modiolus is a fibromuscular structure located at the angles of the mouth, where several facial muscles converge and insert their fibres. The zygomaticus major is one of the muscles that attach to the modiolus, along with the depressor anguli oris, buccinator, risorius, and orbicularis oris muscles. The modiolus plays a crucial role in coordinating the movements of the muscles involved in facial expressions and speech.
The zygomaticus major muscle is part of a group of muscles called the buccolabial group, which also includes the risorius, levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, levator anguli oris, depressor labii inferioris, depressor anguli oris, mentalis, orbicularis oris, incisivus superior, incisivus inferior, and buccinator muscles. These muscles work together to form the structure and carry out the functions of the cheeks and lips, contributing to various facial expressions and speech.
The activity of the zygomaticus major muscle has been studied using facial electromyography (fEMG), which measures the electrical activity underlying muscle movement. Research has shown that the activity of this muscle is linearly related to positive emotions, with increased activity observed in response to more positive stimuli. This has led to the muscle being widely associated with smiling and emotional expression.
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It can be injured by trauma or overuse
The zygomaticus major muscle is a thin, paired facial muscle that extends diagonally from the zygomatic bone to the angle of the mouth. It is responsible for pulling the angle of the mouth superolaterally, contributing to smiling and emotional expression. This muscle is susceptible to injury through trauma or overuse, which can result in pain and impaired function.
Traumatic injuries to the zygomaticus muscle can occur as a result of direct trauma to the face or surgical procedures in the orofacial region. For example, radiofrequency volumetric reduction for the masseter muscle has been associated with zygomaticus muscle paralysis. In some cases, the injury may be localized to the muscle itself, resulting in a muscle tear or strain. This can cause pain and affect the mobility of the mouth, impacting the ability to smile or make certain facial expressions.
Additionally, zygomaticus muscle injuries can be caused by overuse or repetitive strain. This is particularly common in individuals who use their facial muscles extensively, such as those who frequently smile or express emotions with their faces. Overuse can lead to the development of trigger points in the muscle, resulting in pain that radiates upwards along the side of the nose to the forehead. Trigger points in the zygomaticus muscle can also be activated by active overloads or high muscular demands, such as speaking or chewing for extended periods.
The diagnosis of zygomaticus muscle injuries can be challenging due to the small size and complex anatomy of the muscle. Ultrasonography and electromyography (EMG) are valuable tools for detecting injuries and differentiating between muscle and nerve damage. Ultrasonography can reveal abnormalities such as increased muscle echo intensity, while EMG can detect electrical activity and muscle activation, even when there is no overt movement.
The treatment for zygomaticus muscle injuries depends on the underlying cause and severity. In some cases, self-care practices such as rest and self-massage may be sufficient to alleviate tension and trigger points. However, more severe injuries may require medical intervention, such as anti-inflammatory medications or physical therapy. In rare cases, surgical intervention may be necessary to repair extensive muscle damage or reconstruct lost tissue.
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Frequently asked questions
The zygomaticus major is a thin, paired facial muscle that extends diagonally from the zygomatic bone to the angle of the mouth. It is responsible for pulling the angle of the mouth superolaterally, contributing to facial expressions such as smiling, laughing, disdain, contempt, or smugness.
The primary function of the zygomaticus major muscle is to control the movement of the mouth, particularly in smiling and laughing. It raises the upper lip, baring the upper teeth, and deepens the nasolabial furrow. It also coordinates with other muscles to enable various facial expressions and speech.
A good way to remember the zygomaticus major muscle is to associate it with smiling and laughter. Think of it as the muscle that raises the corners of your mouth and creates a smile on your face. Additionally, you can remember it as the muscle responsible for dimples when smiling, as variations in this muscle can cause dimples.
