Logan Steele
The muscles of mastication are a group of muscles that enable functions such as chewing and grinding. These include the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles. Unlike most facial muscles, they are innervated by the mandibular branch of the trigeminal nerve (CN V3). The masseter muscle, for example, is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. The temporalis muscle is a large, flat muscle that lies within the temporal fossa of the skull. While these four muscles are the primary participants in mastication, other muscles help with the process, such as those of the tongue and cheeks, as well as accessory muscles like the buccinator and suprahyoid muscles.
| Characteristics | Values |
|---|---|
| Muscles of mastication | Temporalis, Masseter, Medial Pterygoid, Lateral Pterygoid |
| Muscle functions | Chewing, Biting, Grinding, Moving the jaw |
| Innervation | Motor branches of the mandibular division of the trigeminal nerve (CNV3) |
| Arterial supply | Branches of the maxillary artery |
| Muscle disorders | Myofascial pain, Myositis, Neoplasms, Myospasm, Myofibrotic contracture |
| Accessory muscles | Buccinator, Suprahyoid, Infrahyoid |
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What You'll Learn
- Muscles of mastication are innervated by the mandibular branch of the trigeminal nerve
- The masseter muscle is the most powerful muscle of mastication
- The temporalis muscle is a large, flat muscle that lies within the temporal fossa of the skull
- The buccinator is a facial expression muscle that helps in mastication
- Bruxism is an involuntary, repetitive oral activity characterised by teeth clenching or grinding
Muscles of mastication are innervated by the mandibular branch of the trigeminal nerve
The muscles of mastication are a group of four muscles: the masseter, temporalis, medial pterygoid, and lateral pterygoid. These muscles are responsible for the movement of the lower jaw at the temporomandibular joint (TMJ), enabling functions such as chewing and grinding. The masseter muscle, for instance, is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. It is composed of two layers that differ slightly in their attachments. The temporalis muscle, on the other hand, is a large, flat muscle situated in the temporal fossa. It is fan-shaped and arises from the temporal fossa below the temporal line.
Unlike the muscles of facial expression, which are innervated by the facial nerve (CN VII), the muscles of mastication are innervated by the mandibular branch of the trigeminal nerve (CN V3). The mandibular nerve is the third division of the trigeminal nerve and is the only division that carries motor fibres. It exits the skull through the foramen ovale of the greater wing of the sphenoid bone. The trigeminal nerve, also known as the fifth cranial nerve or CN V, has three main branches: the ophthalmic branch (V1), the maxillary branch (V2), and the mandibular branch (V3).
The temporalis muscle is innervated by the deep temporal branches of the mandibular nerve. The masseter muscle, meanwhile, receives its innervation from the masseteric nerve, a branch of the mandibular nerve. The medial pterygoid muscle is innervated by the medial pterygoid branch of the mandibular nerve. It has two heads, a superficial head and a deep head, with the deep head being larger and originating from the medial surface of the lateral pterygoid plate of the sphenoid bone. Lastly, the lateral pterygoid muscle is innervated by the lateral pterygoid branch of the mandibular nerve. It is the sole muscle responsible for causing depression of the mandible, which is largely the result of gravity.
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The masseter muscle is the most powerful muscle of mastication
The masseter muscle is one of the four muscles of mastication, along with the temporalis, medial pterygoid, and lateral pterygoid muscles. These muscles are responsible for the movement of the jaw, including chewing and grinding. The masseter muscle is the most powerful muscle among them and plays a crucial role in the mastication process.
The masseter muscle is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. It is composed of two layers: a larger, superficial layer and a deep layer. The superficial layer originates from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic arch. The deep layer arises from the medial surface and inferior margin of the zygomatic arch. The muscle fibres converge to form a tendon that attaches to the lateral surface of the mandible and the coronoid process.
The masseter muscle is responsible for the elevation of the mandible, bringing the teeth together during chewing. This is achieved through the contraction of its superior part, which moves the mandible forward. Additionally, the masseter muscle also plays a role in protrusion, or the forward movement of the mandible. The deep fibres of the muscle are important for retracting the mandible, while the superficial fibres aid in protrusion.
The masseter muscle is innervated by the masseteric nerve, a branch of the mandibular nerve (V3) of the trigeminal nerve. Its blood supply is derived from the masseteric artery, a branch of the maxillary artery. Dysfunction of the masseter muscle can lead to pain, difficulty in chewing, and swelling around the jaw and face.
In summary, the masseter muscle is the most powerful muscle of mastication due to its strong quadrangular structure and its crucial role in elevating the mandible and enabling the chewing motion. Its dysfunction can lead to noticeable symptoms, highlighting its importance in maintaining oral health and function.
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The temporalis muscle is a large, flat muscle that lies within the temporal fossa of the skull
The temporalis muscle is a large, fan-shaped muscle that lies within the temporal fossa of the skull. It is one of the muscles of mastication, which are a group of muscles associated with movements of the jaw. The temporalis muscle is the strongest muscle of the temporomandibular joint and plays a crucial role in the act of chewing or grinding.
The temporalis muscle originates from the temporal fossa, which is a broad area of attachment located on the temporal bone of the skull. It passes medial to the zygomatic arch and forms a tendon that inserts onto the coronoid process of the mandible. The muscle fibres converge anteriorly to form this tendon, which runs deep to the zygomatic arch. The temporalis muscle is innervated by the deep temporal branches of the mandibular nerve, specifically the anterior, middle, and posterior deep temporal branches of the anterior trunk of the mandibular nerve (V3).
The primary function of the temporalis muscle is to produce movements of the mandible at the temporomandibular joint. Its anterior portion moves the mandible dorsocranially (elevation), while its posterior fibres pull the mandible backward (retrusion). The unilateral contraction of the temporalis muscle contributes to the side-to-side movements of the jaw during chewing. Additionally, the bilateral contraction of the muscle results in the elevation of the mandible.
The temporalis muscle is covered by the temporal fascia, also known as the temporal aponeurosis. This deep surface of the temporal fascia is also the origin of the muscle, along with the temporal fossa. The temporalis muscle is accessible at the temples and can be observed contracting during jaw clenching and unclenching. The muscle is utilised in certain medical procedures, such as skull base reconstruction and orbital cavity obliteration, due to its proximity to the orbit and anterolateral skull base.
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The buccinator is a facial expression muscle that helps in mastication
The buccinator muscle is a thin, quadrilateral facial muscle that is the main component of the cheek. It is one of the muscles responsible for facial expression. The buccinator muscle is innervated by the buccal branches of the facial nerve (CN VII). The buccal artery, a branch of the maxillary artery, provides the buccinator with its main arterial blood supply.
The buccinator muscle helps in mastication by compressing the cheek against the molar teeth, which keeps food pushed back within the oral cavity. This function is important to prevent food from escaping into the oral vestibule, as well as pushing any food that entered the vestibule back into the oral cavity. The buccinator also prevents the cheeks from being bitten during mastication.
The muscles of mastication are a group of muscles responsible for the chewing movement 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, masseter, medial pterygoid, and lateral pterygoid muscles. These muscles attach to the mandible and produce movements of the lower jaw at the TMJ.
The temporalis muscle is a large, flat muscle that lies within the temporal fossa of the skull. It functions as an elevator of the mandible. The masseter muscle is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. It is composed of two layers that differ slightly in their attachments. The medial pterygoid and lateral pterygoid muscles lie in the infratemporal fossa.
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Bruxism is an involuntary, repetitive oral activity characterised by teeth clenching or grinding
Bruxism is an involuntary, rhythmic oral activity characterised by teeth clenching or grinding. It can occur during sleep or while awake, and it often goes unnoticed by the person affected. Bruxism is a prevalent condition, with sleep bruxism affecting 15% to 40% of children and 8% to 10% of adults, while wake bruxism affects 22.1% to 31% of the population. The condition is associated with powerful forces exerted on the teeth, periodontal structures, temporomandibular joint, and masticatory muscles, which can lead to several issues.
The masseter muscle, one of the primary muscles of mastication, is commonly involved in bruxism. This strong, quadrangular muscle covers the lateral aspect of the ramus of the mandible and plays a crucial role in jaw movements. Bruxism results in rhythmic contractions of the masseter muscle, leading to teeth grinding and mandible thrusting. The temporalis muscle, another muscle of mastication, works in conjunction with the masseter to produce similar movements.
The medial and lateral pterygoid muscles are also part of the muscles of mastication. They contribute to specific jaw movements, such as protrusion, retraction, and side-to-side motions. While these muscles are not directly mentioned in the context of bruxism, their involvement in jaw function suggests they may play a role in the condition.
While the exact cause of bruxism is not fully understood, it is believed to be associated with various factors. Stress, anxiety, sleep disorders, certain medications, and neurologic and psychiatric disorders are considered risk factors for bruxism. Sleep bruxism, in particular, has been linked to underlying medical conditions such as obstructive sleep apnea, Down syndrome, and medication side effects. The condition can cause significant dental issues, including tooth wear, erosion, and destruction, as well as pain in the temporomandibular joint and headaches.
Managing bruxism involves a comprehensive approach, including behavioural techniques, oral devices such as custom mouth guards, pharmacotherapy, counselling, and lifestyle management. Collaboration among healthcare professionals, such as dentists, sleep specialists, and physical therapists, is essential to optimise care for patients with bruxism.
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Frequently asked questions
The muscles of mastication are a group of four muscles that are associated with movements of the jaw. These are the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles.
The muscles of mastication are involved in biting and chewing. The masseter and temporalis muscles are powerful elevators of the mandible, assisted by the pterygoid medialis. The pterygoid lateralis, assisted by the digastric, opens the mouth by depressing and protracting the mandible. The temporalis muscles, working independently on one side, will deviate the jaw outward to the same side.
Unlike most other facial muscles, which are innervated by the facial nerve (CN VII), the muscles of mastication are innervated by the trigeminal nerve (CN V). The mandibular nerve (CN V3) is the largest and inferior-most division of the trigeminal nerve.
