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The mandible is the only bone that moves during mastication (chewing) and other activities such as talking. The muscles of mastication are responsible for the chewing movement of the mandible at the temporomandibular joint (TMJ). They enhance the process of eating, assist in grinding food, and function to approximate the teeth. The lateral pterygoid muscle is the major protractor of the mandible, pushing the jaw forward. Acting unilaterally, the lateral pterygoids produce the ‘side to side’ movement of the jaw.
| Characteristics | Values |
|---|---|
| Muscle Type | Lateral pterygoid muscle |
| Muscle Shape | Triangular |
| Muscle Fibres | Horizontally oriented |
| Function | Protraction (forward movement) of the mandible, abduction (depression), mediotrusion (mandibular condyle movement towards the midline) |
| Activity | Active during mastication and mandibular movements |
| Bilateral Action | Protraction of the mandible, pushing the jaw forward |
| Unilateral Action | 'Side to side' movement of the jaw |
| Assistance | The only muscle of mastication that assists in depressing the mandible (opening the jaw) |
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What You'll Learn
- The lateral pterygoid muscle is the major protractor of the mandible
- The medial pterygoid muscle assists with mandible protrusion
- The masseter muscle has a minor role in mandible protrusion
- The temporalis muscle contributes to side-to-side grinding movements
- The mandible is the only bone that moves during mastication
The lateral pterygoid muscle is the major protractor of the mandible
The mandible is the only bone in the body that moves during mastication (chewing) and other activities such as talking. The muscles of mastication are responsible for the chewing movement of the mandible at the temporomandibular (TMJ) joint. They enhance the process of eating and assist in grinding food, as well as functioning to approximate the teeth.
The masseter muscle is another muscle that is involved in mandibular protrusion. It is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. It is composed of two layers that slightly differ in their attachments. Its larger, superficial layer arises from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic arch. From this origin, these muscle fibres run inferiorly and posteriorly to attach to the lateral surface of the angle and lower half of the ramus of the mandible. The deep layer of the masseter muscle arises from the medial surface and inferior margin of the zygomatic arch. The major function of the masseter muscle is to elevate the mandible, with a minor contribution to protrusion.
The medial pterygoid muscle is also involved in mandibular protrusion. It is a thick, rectangular muscle with a superficial head and a deep head. The deep head arises from the medial surface of the lateral pterygoid plate of the sphenoid bone and the adjacent pyramidal process of the palatine bone. The medial pterygoid muscle fibres converge inferiorly, forming a tendon that inserts on the medial ramus of the mandible posterior and inferior to the mylohyoid groove of the mandible. The insertion of the medial pterygoid forms a tendinous band with the insertion of the masseter called the pterygoid-masseteric sling.
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The medial pterygoid muscle assists with mandible protrusion
The medial pterygoid muscle is a quadrangular muscle situated in the infratemporal fossa. It is composed of two heads, each with two sets of origins. The larger deep head arises from the medial surface of the lateral pterygoid plate of the sphenoid bone and the adjacent pyramidal process of the palatine bone. The smaller superficial head originates from the maxillary tuberosity and pyramidal process of the palatine bone. The medial pterygoid muscle fibres converge inferiorly, forming a tendon that inserts on the medial ramus of the mandible.
The medial pterygoid muscle is innervated by the medial pterygoid branch of the mandibular division of the trigeminal nerve (CN V3). Its blood supply comes from the pterygoid branches of the maxillary artery. The bilateral contraction of this muscle elevates the mandible and closes the mouth. Due to the direction of its muscle fibres, the medial pterygoid muscle pulls the mandible forward, resulting in protrusion. This movement is also known as 'protrusion'.
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 originate from the surface of the skull and attach onto the rami of the mandible at the TMJ. The movements performed by these muscles include elevation, depression, protrusion, retraction, and side-to-side movement.
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The masseter muscle has a minor role in mandible protrusion
The mandible, or lower jaw, is moved by a group of muscles called the muscles of mastication. These muscles enable functions such as chewing and grinding by allowing the mandible to move forward (protrusion), backwards (retraction), up (elevation), down (depression), and side to side.
The masseter muscle is one of the four muscles of mastication, along with the temporalis, medial pterygoid, and lateral pterygoid muscles. It is a powerful, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. The masseter is primarily responsible for elevating the mandible, bringing the teeth together in a chewing motion.
However, the masseter muscle also has a minor role in mandible protrusion, or forward movement. This is achieved through the contraction of its superior, or superficial, part. The superficial fibres of the masseter function to protrude the mandible, while the intermediate and deep fibres function to retract it.
The medial pterygoid muscle also contributes to mandible protrusion. It assists with the elevation and protrusion of the mandible, as well as side-to-side mandibular motion during grinding. The lateral pterygoid muscle, on the other hand, is the major protractor of the mandible. It is the only muscle of mastication that assists in depressing the mandible (opening the jaw).
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The temporalis muscle contributes to side-to-side grinding movements
The temporalis muscle, also known as the temporal muscle, is one of the muscles responsible for mastication (chewing). It is a broad, fan-shaped convergent muscle found on each side of the head, filling the temporal fossa and covering much of the temporal bone. The temporalis muscle fibres converge inferiorly, forming a tendon that inserts on the coronoid process of the mandible. This muscle is innervated by the deep temporal nerve, a branch of the mandibular nerve, and receives its blood supply from the deep temporal arteries, which anastomose with the middle temporal artery.
The temporalis muscle has several functions, including elevating the mandible, retracting the mandible, and contributing to side-to-side grinding movements. The elevation of the mandible is facilitated by the anterior vertical fibres of the muscle, which are constantly active, working against gravity to keep the mouth closed. On the other hand, the contraction of the posterior, more horizontal fibres of the muscle results in the retraction of the mandible, pulling the jaw backwards.
The side-to-side grinding movement is a crucial function of the temporalis muscle. This movement is part of the mastication process, where the muscles of mastication work together to grind food and approximate the teeth. The temporalis muscle, along with other muscles such as the medial pterygoid and lateral pterygoid, contribute to these side-to-side mandibular motions during chewing. These muscles ensure that the mandible can move from side to side, enabling the grinding action necessary for breaking down food during mastication.
The complex structure of the temporalis muscle allows it to play a significant role in both the elevation and retraction of the mandible, as well as the side-to-side grinding movements. The muscle's broad area of attachment and its insertion onto the coronoid process of the mandible enable it to produce these diverse movements. The temporalis muscle is also unique in that it is accessible at the temples, allowing individuals to visually observe and feel the muscle contracting during jaw clenching and unclenching.
In summary, the temporalis muscle contributes to side-to-side grinding movements as part of its role in mastication. This muscle, along with others in the masticatory system, ensures that food is effectively ground and chewed, facilitating the process of eating. The specific functions of the temporalis muscle, including elevation, retraction, and side-to-side movements, work in harmony to enable efficient chewing and grinding, making it a crucial component of oral physiology.
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The mandible is the only bone that moves during mastication
The movement performed by these muscles includes elevation, depression, protrusion, retraction, and side-to-side movement. Three out of the main muscles are responsible for adduction of the mandible, while one helps in the abduction of the mandible. The muscles of mastication are innervated by motor branches of the mandibular division of the trigeminal nerve (CNV3), while the main arterial supply is derived from branches of the maxillary artery.
The masseter muscle, for example, is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. Its major function is to elevate the mandible, with a minor contribution to protrusion. The medial pterygoid muscle, on the other hand, assists with elevation and protrusion of the mandible, as well as side-to-side mandibular motion for grinding food.
The lateral pterygoid muscle is triangular in shape and has two heads: superior and inferior. It is the primary muscle responsible for depression of the mandible, as well as assisting with protrusion and side-to-side movement. The temporalis muscle also contributes to grinding movements by moving the mandible from side to side.
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Frequently asked questions
The lateral pterygoid muscle is the major protractor of the mandible, allowing for forward movement of the jaw.
The lateral pterygoid muscle has a triangular shape and two heads: superior and inferior. It is active during mastication and mandibular movements, including protrusion, abduction and mediotrusion. It is also active during speaking, singing and clenching.
Mastication is the process of chewing food, which involves the coordinated action of various muscles in the jaw. The mandible is the only bone that moves during this process.
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: masseters, temporalis, and pterygoids.
The masseter muscle is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. Its major function is to elevate the mandible, with a minor contribution to the protrusion of the mandible.
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