Maximus Gage
The muscles responsible for mandibular movement are the primary muscles of mastication: the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. These muscles attach to the rami of the mandible and facilitate biting and
| Characteristics | Values |
|---|---|
| Muscles Involved | Temporalis, Medial Pterygoid, Lateral Pterygoid, Masseter, Digastric, Mylohyoid, Geniohyoid |
| Muscle Origin | Skull Bones |
| Muscle Insertion | Various Features of the Mandible |
| Innervation | Mandibular Nerve (CN V3), Trigeminal Nerve (CN V) |
| Blood Supply | Maxillary Artery, Masseteric Artery |
| Function | Elevation, Depression, Protrusion, Retraction, Side-to-Side Movement, Opening and Closing the Mouth |
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What You'll Learn
The role of the masseter muscle
The masseter muscle is a large, rectangular muscle located on both sides of the face, extending from the cheekbone down to the angle of the mandible. It is one of the four main muscles of mastication (chewing), along with the temporalis, medial pterygoid, and lateral pterygoid muscles. These muscles attach to the rami of the mandible and work together to produce mandibular movements for chewing food.
The masseter muscle has a crucial role in elevating the mandible, allowing for the closing of the mouth. It also assists in protruding the mandible, bringing the lower front teeth in front of the upper front teeth. This protrusive action is primarily performed by the superficial fibres of the masseter muscle. In contrast, the intermediate and deep muscle fibres of the masseter contribute to retracting the mandible, pulling the jaw backward. The deep fibres also play a stabilising role for the TMJ (temporomandibular joint).
The masseter muscle receives nerve input from the masseteric nerve, a branch of the mandibular nerve, which is the third division of the trigeminal nerve. The blood supply for the masseter muscle is derived from the masseteric artery, a branch of the maxillary artery. The nerve supply is essential for the muscle to perform its intended movements, as motor neurons innervate the muscle fibres.
The masseter muscle is subject to various conditions that can impact its function. For example, strong and persistent spasms of the masseter muscle can occur during an infection with the bacteria Clostridium tetani, a condition known as trismus that interferes with normal feeding. Singers may also experience masseter tension, which can be alleviated through transdermal massages or stretches as part of their vocal warm-up routine.
The masseter muscle is unique to mammals and plays a vital role in the mastication process. Its positioning and structure enable it to elevate and protrude the mandible, facilitating the chewing of food. The masseter muscle works in coordination with the other muscles of mastication to produce the complex movements required for chewing and grinding food effectively.
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The temporalis muscle
The main function of the temporalis muscle is to produce the movements of the mandible at the temporomandibular joint and thus facilitate the act of mastication. The contraction of the anterior fibres of the muscle moves the mandible dorsocranially (elevation) while the contraction of the posterior fibres pulls the mandible posteriorly (retrusion). The contraction of the posterior fibres of the temporalis muscle results in the backward movement of the mandible. In unison, these actions facilitate the closing of the mouth and the approximation of the teeth. Additionally, the unilateral contraction of the temporalis muscle plays an important role in the side-to-side movements of the jaw.
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Medial pterygoid muscle
The medial pterygoid muscle is a thick rectangular or square-shaped muscle with two heads: a deep head and a superficial head. The deep head is larger and originates 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 of the inferior maxilla. The medial pterygoid muscle is located in the infratemporal fossa, lying deep to the masseter and temporalis muscles. It is one of the four main muscles of mastication (chewing food), along with the lateral pterygoid, masseter, and temporalis muscles.
The medial pterygoid muscle is innervated by the medial pterygoid nerve, a branch of the mandibular nerve (CN V3), which is itself a branch of the trigeminal nerve (CN V). The medial pterygoid nerve supplies the medial pterygoid muscle before dividing into the trigeminal nerve, unlike the other muscles of mastication, which are supplied by the anterior division of the mandibular nerve. The medial pterygoid muscle receives its blood supply from the pterygoid and buccal branches of the maxillary artery, as well as the facial artery through its muscular branches.
The medial pterygoid muscle has several functions, including elevating the mandible (closing the mouth), protruding the mandible, and assisting with mastication, especially when the maxillary and mandibular teeth are close together. It also assists with side-to-side mandibular motion, which helps with grinding food during chewing. Unilateral contraction of the medial pterygoid muscle causes a slight medial rotation of the mandible, and when this occurs simultaneously with the contraction of the ipsilateral lateral pterygoid muscle, it results in a noticeable movement of the mandible swinging anteriorly and medially. Bilateral contraction of the medial pterygoid muscle with the lateral pterygoid muscle results in protrusion of the mandible, while unilateral contraction of the medial pterygoid muscle with the lateral pterygoid muscle on the same side results in lateral movement of the mandible towards the opposite side.
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Lateral pterygoid muscle
The lateral pterygoid muscle is a craniomandibular muscle that plays a crucial role in mandibular movements, including protrusion (forward movement of the mandible), abduction (depression of the mandible), and mediotrusion (mandibular condyle movement towards the midline). It is one of the four muscles of mastication, along with the medial pterygoid, temporalis, and masseter muscles. These muscles act on the temporomandibular joint (TMJ) to enable chewing and biting.
The lateral pterygoid muscle is located deep to the temporalis and masseter muscles, spanning between the sphenoid bone and the temporomandibular joint. It is a two-headed, fan-shaped muscle, with the upper and lower heads originating from different parts of the sphenoid bone. The upper head arises from the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone, while the lower head originates from the lateral surface of the lateral pterygoid plate of the sphenoid bone.
The lateral pterygoid muscle is innervated by the lateral pterygoid nerve, a branch of the mandibular nerve (CN V3), which is itself a branch of the trigeminal nerve (CN V). The primary function of the lateral pterygoid muscle is to protrude the mandible by pulling the head of the condyle out of the mandibular fossa along the articular eminence. A unilateral contraction of the lateral pterygoid muscle, in conjunction with the ipsilateral medial pterygoid muscle, moves the mandible to the opposite side, allowing for alternating side-to-side movements during chewing.
The lateral pterygoid muscle is also involved in depressing the mandible and opening the jaw. It is the only muscle among the four muscles of mastication that participates in depressing the mandible. When both bellies of the lateral pterygoid muscle contract bilaterally, the mandible moves forward (protrusion). The lateral pterygoid muscle is supplied by the pterygoid branches of the maxillary artery.
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Accessory muscles of mastication
The muscles of mastication are a group of muscles that enable the movement of the mandible during chewing and speech. They control the opening and closing of the mouth and play a role in the configuration of the face. These muscles can be divided into primary and secondary or accessory muscles. The primary muscles of mastication include the temporalis, masseter, lateral pterygoid, and medial pterygoid muscles.
The accessory muscles of mastication include the buccinator, suprahyoid, and infrahyoid muscles. The suprahyoid muscles include the digastric muscle, mylohyoid muscle, and geniohyoid muscle. The infrahyoid muscles include the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles. These accessory muscles work in coordination with the primary muscles to produce mandibular movement for chewing food.
The temporalis muscle is a fan-shaped muscle that fills the temporal fossa. Its anterior and mid fibres elevate the mandible, while its posterior fibres retract the mandible. The temporalis muscle also contributes to side-to-side grinding movements. The masseter muscle is responsible for elevating the mandible and approximating the teeth. Its intermediate and deep muscle fibres retract the mandible, while the superficial fibres protrude the mandible.
The medial pterygoid muscle assists with the elevation and protrusion of the mandible, as well as side-to-side mandibular motion for grinding food. The lateral pterygoid muscle, depending on the degree of its contraction, can protrude and depress the mandible or move it from side to side during chewing.
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Frequently asked questions
The primary muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles.
The temporalis muscle functions to elevate the mandible, retract the mandible, and contribute to side-to-side grinding movements.
The masseter muscle functions to elevate the mandible, approximate the teeth, retract the mandible, and protrude the mandible.
The medial pterygoid muscle functions to assist with elevation and protrusion of the mandible, as well as side-to-side mandibular motion for grinding food.
The functions of the lateral pterygoid muscle depend on the degree of its contraction. Bilateral contraction protrudes and depresses the mandible, while unilateral contraction moves the mandible to the opposite side, allowing for side-to-side movements during chewing.
