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The muscles of mastication, or chewing muscles, are a group of muscles that enable chewing and grinding movements of the mandible at the temporomandibular joint (TMJ). The four main chewing muscles are the temporalis, masseter, medial pterygoid, and lateral pterygoid muscles. These muscles work together with other muscles, such as those in the tongue and cheeks, to produce mandibular movements such as elevation, depression, protrusion, retraction, and side-to-side movement.
| Characteristics | Values |
|---|---|
| Number of muscles | 4 |
| Muscle names | Temporalis, Masseter, Medial Pterygoid, Lateral Pterygoid |
| Muscle shape | Fan-shaped, triangular, quadrangular |
| Muscle origin | Skull, temporal fossa, zygomatic bone, infratemporal fossa |
| Muscle insertion | Mandible, jaw |
| Muscle nerve supply | Trigeminal nerve, mandibular nerve |
| Muscle arterial supply | Maxillary artery |
| Muscle movement | Elevation, depression, protrusion, retraction, side-to-side movement |
| Muscle function | Chewing, grinding, abduction/adduction of mandible |
| Muscle disorders | Myofascial pain, myositis, neoplasms, bruxism |
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What You'll Learn
The four main chewing muscles
The muscles of mastication are a group of muscles that enable chewing and grinding movements of the mandible at the temporomandibular (TMJ) joint. They enhance the process of eating and assist in grinding food. The four main muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. These muscles originate from the surface of the skull and attach to the rami of the mandible at the TMJ.
The temporalis muscle is a fan-shaped muscle that fills the temporal fossa. It originates from the temporal fossa to the inferior temporal line of the lateral skull. The fibres of the temporalis muscle converge inferiorly, forming a tendon that exits the temporal fossa and attaches to the jaw. The temporalis muscle elevates and retracts the jaw.
The lateral pterygoid muscle has a triangular shape with two heads, superior and inferior. It is the major protractor (opener) of the jaw. Both heads originate adjacent to the eye socket and converge into a tendon that attaches to the jaw. The lateral pterygoids work together to protract the jaw and independently to produce lateral movement.
The medial pterygoid muscle has a quadrangular shape with two heads, deep and superficial. It is located inferior to the lateral pterygoid. The superficial head originates from the front of the skull, while the deep head attaches to the skull near the eye socket. The medial pterygoid is involved in the protrusion of the mandible.
The masseter muscle is the most powerful muscle of mastication. It is quadrangular in shape and split into two regions, deep and superficial. The superficial region originates from the skull below the eye socket, while the deep region originates from the skull above the jaw. Both parts attach to the jaw and elevate it.
In addition to the four main muscles of mastication, there are accessory muscles that also help with the process of chewing, such as the muscles of the tongue and the cheeks.
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Accessory chewing muscles
The muscles of mastication are a group of muscles that enable chewing by moving the mandible (jawbone) at the temporomandibular joint (TMJ). These muscles work to elevate, depress, protrude, retract, and move the mandible side to side. The four primary muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles.
The primary muscles work in coordination with the secondary or accessory muscles of mastication to produce mandibular movement for chewing food. The accessory muscles of mastication include the buccinator, suprahyoid muscles, and infrahyoid muscles.
The buccinator is a facial expression muscle that helps in mastication by keeping food pushed back within the oral cavity. The suprahyoid muscle group is made up of the digastric muscle, mylohyoid muscle, and geniohyoid muscle. They depress the mandible against resistance when the infrahyoid muscles fix or depress the hyoid bone. The infrahyoid muscles include the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles.
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Chewing muscle disorders
The muscles of mastication are a group of muscles responsible for the movement of the mandible at the temporomandibular joint (TMJ). They enhance the process of eating by assisting in grinding food. The four main muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. These muscles work together to produce movements such as elevation, depression, protrusion, retraction, and side-to-side movement of the jaw.
Myofascial pain and dysfunction are characterised by a dull, aching pain in the jaw and temple muscles, often with trigger points that produce referred pain when palpated. It can be caused by nocturnal bruxism (teeth grinding during sleep), habitual clenching of the mouth, or whiplash injuries. Temporomandibular joint (TMJ) dysfunction is a common result of myofascial pain, leading to an imbalance in the forces within the muscles of mastication.
Myositis is an inflammatory condition of the muscles that can be caused by trauma or infection. It is characterised by swelling, redness, and increased temperature in the affected area, resulting in jaw dysfunction and limited range of motion.
Bruxism is a disorder characterised by involuntary, repetitive teeth clenching or grinding. It can occur during sleep or wakefulness and can arise from various psychological, neurological, or orodental conditions.
In summary, chewing muscle disorders encompass a range of conditions affecting the muscles of mastication. These disorders can cause pain, dysfunction, and limited mobility in the jaw and associated muscles. Proper diagnosis and treatment are crucial to alleviate symptoms and restore normal function.
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Chewing muscle pain
The muscles responsible for the act of chewing are called the muscles of mastication. They are a group of four muscles that originate from the surface of the skull and attach to the mandible (lower jaw) at the temporomandibular joint (TMJ). The four muscles are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. These muscles work together to produce the mandibular movements of mastication, which include elevation, depression, protrusion, retraction, and side-to-side movement.
- Teeth grinding (bruxism), which can lead to TMJ dysfunction.
- Gum (periodontal) disease, an infection caused by poor dental hygiene.
- Toothache, which may be a result of dental caries or other dental issues.
- Arthritis, which can cause inflammation and breakdown of the temporomandibular joint.
- Trauma, such as a broken or dislocated jaw, which requires immediate medical attention.
- Masticatory myofascial pain, characterised by trigger points that produce referred pain and increase during function.
- Myositis, an inflammatory condition caused by trauma or infection, resulting in swelling, redness, increased temperature, and limited jaw movement.
If you are experiencing jaw or chewing muscle pain, it is recommended to consult a healthcare professional, especially if the pain lasts more than a week or is severe. Treatment options may include mouth guards, orthodontics, stress management, or simple remedies such as eating soft foods, applying heat or cold, and taking over-the-counter anti-inflammatory medications.
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Chewing muscle nerve supply
The muscles of mastication are a group of muscles responsible for the chewing movement of the mandible at the temporomandibular joint (TMJ). They enhance the process of eating and assist in grinding food. The four main muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. Unlike the muscles of facial expression, which are innervated by the facial nerve (CN VII), the muscles of mastication are innervated by motor branches of the mandibular division of the trigeminal nerve (CNV3). The mandibular nerve is the largest and most inferior division of the trigeminal nerve (CN V). It is the only division of the trigeminal nerve that carries motor fibres, and it also contains sensory fibres.
The masseter muscle is the most powerful muscle of mastication. It is innervated by the masseteric nerve, a branch of the mandibular nerve. Its blood supply is derived from the masseteric artery, which emerges from the maxillary artery. The major function of the masseter muscle is to elevate the mandible, with a minor contribution to protrusion of the mandible. The intermediate and deep muscle fibres of the masseter function to retract the mandible, while the superficial fibres function to protrude it. The deep fibres are important stabilisers of the TMJ.
The temporalis muscle is a fan-shaped muscle that fills the temporal fossa. It originates from the temporal fossa to the inferior temporal line of the lateral skull. The temporalis muscle fibres converge inferiorly, forming a tendon that exits the temporal fossa, passing underneath the zygomatic arch, and inserting on the coronoid process of the mandible. It is supplied by the deep temporal nerve, a branch of the anterior division of the mandibular nerve. The function of the anterior and mid fibres of the temporalis muscle is to elevate the mandible, while the posterior fibres function to retract the mandible. The temporalis muscle also contributes to side-to-side grinding movement.
The medial pterygoid muscle is a thick, rectangular muscle with a superficial head and a deep head. It is innervated by the medial pterygoid branch of the mandibular nerve. Its principal blood supply stems from the pterygoid branches of the maxillary artery. The major functions of this muscle are elevation of the mandible, protrusion of the mandible, and side-to-side movements when grinding and chewing.
The lateral pterygoid muscle is a triangular muscle that lies in the infratemporal fossa. It is the major protractor (opener) of the jaw. It is innervated by the lateral pterygoid branch of the mandibular nerve and vascularized by the pterygoid branches of the maxillary artery. The function of the lateral pterygoid depends on the degree of its contraction. Bilateral contraction of the lateral pterygoid muscles protrudes and depresses the mandible. A unilateral contraction on a particular side, in conjunction with the ipsilateral medial pterygoid muscle, moves the mandible to the opposite side. This allows for alternating side-to-side movements during chewing.
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Frequently asked questions
The chewing muscles, also known as the muscles of mastication, are a group of muscles that enable the movement of the lower jaw, allowing functions like chewing and grinding food.
There are four primary muscles of mastication: the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles.
The main functions of the chewing muscles are to produce movements such as elevation, depression, protrusion, retraction, and side-to-side movement of the mandible (lower jaw).
The temporalis muscle is located in the temporal fossa, the masseter muscle is in the cheek area, and the medial and lateral pterygoid muscles are found in the infratemporal fossa.
Yes, disorders such as myofascial pain, myositis, bruxism, and TMJ (temporomandibular joint) dysfunction are related to the chewing muscles. These disorders can cause pain, limited jaw movement, and teeth grinding.
