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The masseter muscle is a powerful, thick, and rectangular muscle that is essential for chewing and eating. It is one of the four primary muscles of mastication, along with the temporalis, lateral pterygoid, and medial pterygoid muscles. The masseter muscle originates from the zygomatic arch and extends down to the mandibular angle, with both superficial and deep parts. Its main function is to elevate the mandible, causing a powerful jaw closure, and it also assists in the protrusion or forward movement of the lower jaw. The masseter muscle is well-conserved across the human population and is also found in many animals, with some variations in shape and function.
| Characteristics | Values |
|---|---|
| Name | Masseter Muscle |
| Origin | The muscle originates from the zygomatic arch and maxillary process of the zygomatic bone. |
| Insertion | The muscle inserts along the angle and lateral surface of the mandibular ramus. |
| Action | The masseter muscle is responsible for elevating the mandible, causing a powerful jaw closure. It also aids in the protrusion of the mandible, allowing for the forward movement of the jaw. |
| Blood Supply | The masseter muscle receives its blood supply primarily from the masseteric artery, a branch of the maxillary artery. |
| Innervation | The masseter muscle is innervated by the mandibular division of the trigeminal nerve, also known as the masseteric nerve. |
| Function | The masseter muscle is one of the muscles of mastication or chewing. It helps in elevating the mandible, closing the jaw, and moving the mandible forward. |
| Shape | The masseter muscle has a quadrangular or rectangular shape with two divisions: superficial and deep. |
| Hypertrophy | Masseter hypertrophy refers to the enlargement of the masseter muscle, resulting in a square jawline shape. It is often asymptomatic but can cause aesthetic concerns. |
| Treatment | Treatment options for masseter hypertrophy include conservative therapies, behaviour therapy, botulinum toxin injections, and surgical procedures. |
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What You'll Learn
- The masseter muscle is one of the four muscles of mastication
- It elevates the mandible, causing a powerful jaw closure
- The masseter muscle has two divisions: superficial and deep
- Masseter muscle hypertrophy refers to the enlargement of the masseter muscle
- The muscle is supplied with blood by the masseteric artery
The masseter muscle is one of the four muscles of mastication
The masseter muscle is supplied with blood by the masseteric artery, a branch of the maxillary artery. It is innervated by the masseteric nerve, a branch of the mandibular nerve (V3) of the trigeminal nerve. The mandibular nerve carries both sensory and motor fibres. The masseter muscle is a paired muscle, meaning that there are two masseter muscles in the human body, one on each side of the jaw.
The masseter muscle is relatively well-conserved across the human population and the animal kingdom. However, one notable difference is masseteric hypertrophy, which is characteristic in populations of Asian descent. Masseteric hypertrophy is a benign condition characterised by an enlargement of the masseter muscles, leading to a square jawline shape. This condition is often a target for aesthetic treatments and Botox requests.
The masseter muscle can become enlarged in individuals who habitually clench or grind their teeth, or even in those who constantly chew gum. This enlargement is usually asymptomatic and soft, and it can be unilateral or bilateral. Even if the enlargement is bilateral, asymmetry of the face may still occur due to unequal enlargement of the muscles. This condition may be confused with other medical issues, such as parotid salivary gland disease, dental infections, and maxillofacial neoplasms.
The masseter muscle is important in the field of physiotherapy, particularly in treating TMD (temporomandibular disorder). Dysfunction of the masseter muscle can result in pain, difficulty chewing, or swelling around the jaw and face. Physiotherapy treatments for TMD may include manual therapy techniques such as trigger point release, massage, and stretching, as well as exercises to improve the range of motion of the jaw.
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It elevates the mandible, causing a powerful jaw closure
The masseter muscle is a powerful muscle that plays a crucial role in our daily lives. It is one of the four primary muscles of mastication (chewing) and is responsible for elevating the mandible, resulting in a powerful jaw closure. This muscle helps us chew and eat our food by moving the mandible forward, known as protrusion or protraction. The masseter muscle is a paired, thick, and rectangular muscle with two divisions: superficial and deep. The superficial portion originates from the zygomatic bone, specifically the zygomatic arch and maxillary process, while the deep portion arises from the entire surface of the zygomatic arch. These fibres converge to insert onto the angle and lateral surface of the mandibular ramus, allowing for the elevation and protrusion movements.
The masseter muscle has a distinct quadrangular shape due to its origins and insertions. It is covered by a strong masseteric fascia on its entire superficial (lateral) aspect. The medial or inner surface of the muscle relates to the ramus of the mandible, almost completely covering its superficial surface. The masseter muscle is a well-conserved muscle across the human population and the animal kingdom. However, masseteric hypertrophy, or enlargement of the masseter muscle, can occur, resulting in a square jawline shape. This condition is often asymptomatic but can cause aesthetic concerns, especially in females or those seeking a more balanced facial appearance.
The masseter muscle's function in elevating the mandible is crucial for jaw closure during chewing. The contraction of the superior part of the muscle moves the mandible forward, allowing for the protrusion movement. Additionally, the deep and intermediate fibres of the masseter muscle retract the mandible, pulling the teeth into an overbite position. Conversely, the superficial fibres protrude the mandible, bringing it forward into an underbite position. This coordination between the muscle fibres ensures a smooth and controlled chewing motion.
The masseter muscle works in conjunction with other jaw-closing muscles, including the temporalis and the lateral and medial pterygoid muscles. Together, they elevate the mandible and close the jaw, bringing the teeth together during chewing. The masseter muscle also plays a stabilising role at the temporomandibular joint (TMJ). When an individual clenches their teeth, the muscle contracts to maintain the correct position of the TMJ. This stabilisation helps prevent disorders such as temporomandibular joint dysfunction (TMD), which can cause pain, chewing difficulties, and swelling in the jaw and face.
The masseter muscle is susceptible to various conditions, including trauma and TMD. Trauma to the face or jaw can result in a fracture, leading to severe pain and swelling. TMD, on the other hand, is a disorder affecting the jaw muscles, temporomandibular joints, and associated nerves, causing chronic facial pain. Treatment for TMD involves managing stress, behavioural therapy, and, in some cases, botulinum toxin injections to reduce muscle contractions. Understanding the role of the masseter muscle in jaw movement and stability is essential for maintaining oral health and treating related conditions effectively.
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The masseter muscle has two divisions: superficial and deep
The masseter muscle is a large muscle found on both sides of the face, extending from the cheekbone down to the angle of the jaw. It is one of the four muscles responsible for mastication (chewing). The masseter muscle has two divisions: the superficial and the deep.
The superficial portion of the masseter muscle originates from a thick aponeurosis on the temporal process of the zygomatic bone and the anterior two-thirds of the inferior border of the zygomatic arch. The fibres of the superficial portion pass inferior-posteriorly over the deep portion and insert into the angle of the mandible and the inferior half of the lateral surface of the ramus of the mandible. The superficial head, the larger of the two, is covered by the parotid gland. The superficial part of the masseter functions to move the mandible or lower jaw forward.
The deep portion of the masseter muscle originates from the entire surface of the zygomatic arch. The fibres run inferiorly and insert along the mandibular ramus superior to the masseter muscle’s superior portion. The deep head is smaller and more muscular in texture. Its function is to allow the mandible or lower jaw to elevate, allowing for the mouth to close.
The masseter muscle is innervated by the anterior division of the mandibular division (V3) of the trigeminal nerve. The blood supply to the masseter muscle is provided by the masseteric artery, a branch of the maxillary artery.
The masseter muscle can become enlarged in patients who habitually clench or grind their teeth, or even in those who constantly chew gum. This condition is called masseteric hypertrophy and results in a square jawline shape.
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Masseter muscle hypertrophy refers to the enlargement of the masseter muscle
The masseter muscle is one of the four muscles of mastication, or chewing. It is a powerful, thick, and rectangular muscle that originates from the zygomatic arch and extends down to the mandibular angle. The masseter muscle is responsible for the elevation of the mandible, causing a powerful jaw closure, and some protraction of the mandible.
The masseter muscle can become enlarged due to being overworked. Some common factors that can contribute to this include emotional stress, chronic clenching or grinding (bruxism), and repetitive habits such as gum chewing. Masseteric hypertrophy is characterised by a benign enlargement of the masseter muscles, leading to a square jawline shape. This can create a more masculine look, especially in female patients, or a bottom-heavy appearance. In cases of unilateral masseter hypertrophy, it can cause jaw asymmetry.
While masseter muscle hypertrophy is not life-threatening, it can cause psychological distress due to the exaggerated appearance of the muscle in the face. Patients may seek treatment for aesthetic concerns, such as Botox or facelift procedures. However, surgery near the masseters requires careful consideration to avoid damaging nearby structures, such as the masseteric ligament, risorius muscle fibres, and branches of the facial nerve.
In summary, masseter muscle hypertrophy refers to the enlargement of the masseter muscle, which can lead to a square jawline and psychological distress due to the noticeable appearance of the muscle. Treatment options are available, ranging from conservative therapy to surgical procedures, but careful consideration is necessary due to the complex anatomy of the region.
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The muscle is supplied with blood by the masseteric artery
The masseter muscle is a strong, thick, and rectangular muscle that is one of the four muscles of the masticatory apparatus. It originates from the zygomatic arch and extends down to the mandibular angle. The muscle is responsible for elevating the mandible, causing a powerful jaw closure, and also provides support to the articular capsule of the temporomandibular joint.
The masseter muscle is supplied with blood by the masseteric artery, a small branch of the maxillary artery. The masseteric artery passes laterally through the mandibular notch to the deep surface of the masseter muscle. It anastomoses with the masseteric branches of the external maxillary artery and the transverse facial artery. The maxillary artery provides blood supply to various structures within the head and face, including the maxilla and mandible, deep facial areas, and the nasal cavity.
The masseter muscle has two divisions: the superficial part and the deep part. The superficial part of the muscle originates from the maxillary process of the zygomatic bone and runs inferoposteriorly to the masseteric tuberosity on the lower part of the ramus of the mandible. The deep part of the muscle consists of vertically directed muscle fibres that originate from the zygomatic arch.
The masseter muscle can become enlarged in individuals who habitually clench or grind their teeth, a condition known as masseteric hypertrophy. This enlargement can lead to a square jawline shape and is often a target for aesthetic treatments or Botox. Singers are also prone to experiencing masseter tension, which can be treated with transdermal massages or stretches as a vocal warm-up.
The masseter muscle plays a crucial role in mastication, or chewing, and its specific functions include the elevation and protrusion of the mandible. Its contraction moves the mandible forward, allowing for the anterior motion of the jaw. The muscle also helps stabilize the tension of the articular capsule of the temporomandibular joint.
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Frequently asked questions
The masseter is one of the four primary muscles responsible for the action of mastication (chewing). It is a powerful, thick, and rectangular muscle with two divisions: superficial and deep.
The masseter muscle helps elevate the lower jaw/mandible and assist in the protrusion/forward movement of the lower jaw. It works with the temporalis and lateral and medial pterygoid muscles to perform this function.
Masseter muscle hypertrophy refers to the enlargement of the masseter muscle. This condition was first described in 1880 and is considered rare. It is often asymptomatic but can cause psychological distress due to the exaggerated appearance of the muscle in the face.
The exact cause of masseter muscle hypertrophy is unknown, but emotional stress and chronic clenching/grinding are common factors that can contribute to overworking the masseter muscles.
