Logan Steele
The muscles of mastication are associated with movements of the jaw. There are four primary muscles of mastication: the masseter, temporalis, medial pterygoid, and lateral pterygoid. The masseter is a powerful muscle that elevates the mandible, causing the mouth to close. The temporalis muscle also closes the mandible. The medial pterygoid is responsible for closing and lateral movements of the mandible, while the lateral pterygoid opens the jaw and allows for side-to-side movement.
| Characteristics | Values |
|---|---|
| Muscles that open the jaw | Anterior digastric, mylohyoid, and inferior head of the lateral pterygoid |
| Jaw-closing muscles | Masseter, temporalis, medial pterygoid, and superior head of the lateral pterygoid |
| Muscle that opposes other muscles of mastication and allows for depression of the mandible | Lateral pterygoid |
| Muscle that allows for the protraction of the mandible and anterior motion of the jaw | Lateral pterygoid |
| Most powerful muscle of mastication | Masseter |
| Muscle that allows for the elevation of the mandible and some protraction of the mandible | Masseter |
| Muscle that receives motor innervation from the mandibular division of the trigeminal nerve | Masseter |
| Muscle that is innervated by CN V and devoted to opening the jaw | Cranial belly of the digastricus |
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What You'll Learn
- The masseter muscle is one of four muscles of mastication and is responsible for jaw elevation
- The medial pterygoid muscle is responsible for jaw closing and lateral movement
- The lateral pterygoid muscle is responsible for jaw opening, deviation, and anterior movement
- The anterior digastric, mylohyoid, and inferior head of the lateral pterygoid are muscles that open the jaw
- Accessory muscles that aid in jaw opening include the digastric, geniohyoid, and mylohyoid
The masseter muscle is one of four muscles of mastication and is responsible for jaw elevation
The masseter muscle is one of four muscles of mastication, which are associated with movements of the jaw. These muscles develop from the first pharyngeal arch and are therefore innervated by a branch of the trigeminal nerve, the mandibular nerve. The masseter muscle is a powerful, superficial quadrangular muscle with two divisions: superficial and 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 masseter muscle is the most powerful muscle of mastication. It is responsible for the elevation of the mandible, causing the mouth to close. Its insertion along the angle and lateral surface of the ramus also allows it to aid in the protrusion of the mandible, enabling anterior motion of the jaw. The masseter muscle can exert very high forces through the recruitment of multiple motor units. This muscle is also capable of exerting very low forces with incredible precision, such as during speech.
The other three muscles of mastication are the temporalis, medial pterygoid, and lateral pterygoid muscles. The temporalis muscle is involved in jaw-closing, while the medial pterygoid muscle contributes to both jaw-closing and lateral movements of the mandible. The lateral pterygoid muscle is the only muscle that actively opposes the other muscles of mastication, allowing for depression of the mandible and the opening of the jaw.
Jaw opening is facilitated by several accessory muscles, including the digastric, geniohyoid, mylohyoid, omohyoid, and stylohyoid muscles. These muscles work in pairs and coordinate the integration of mandibular movement during opening and closing by attaching to the hyoid bone, mandible, and other bones. The hyoid bone, located beneath the mandible, serves as an attachment point for muscles and ligaments that connect the mandible with other structures.
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The medial pterygoid muscle is responsible for jaw closing and lateral movement
The jaw is a complex joint that allows for a wide range of movements, including opening and closing, lateral movement, protrusion, and retraction. This movement is facilitated by several muscles, including the medial pterygoid muscle, which plays a crucial role in jaw closing and lateral movement.
The medial pterygoid muscle is a thick quadrilateral muscle that arises from two heads: a superficial head and a deep head. The superficial head originates from the maxillary tuberosity, while the deep head originates from the medial surface of the lateral pterygoid plate of the sphenoid bone. These muscle fibres converge to form a tendon that inserts on the medial ramus of the mandible, just posterior and inferior to the mylohyoid groove.
The primary function of the medial pterygoid muscle is to assist in the elevation and protrusion of the mandible, which essentially means closing the mouth and moving the jaw forward. This is achieved through bilateral contraction of the muscle, causing the mandible to elevate. In addition, the medial pterygoid muscle also contributes to lateral movement of the mandible. When contracting unilaterally, it works together with the lateral pterygoid muscle to swing the mandible to the opposite side. This lateral movement is essential for chewing and other functional and parafunctional lateral excursive movements.
The medial pterygoid muscle is innervated by the mandibular division of the trigeminal nerve (CN V3). Its blood supply comes from the pterygoid branches of the maxillary artery. Understanding the anatomy and function of the medial pterygoid muscle is important, as any disturbances or spasms in this muscle can lead to issues with jaw movement and even result in a locked jaw.
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The lateral pterygoid muscle is responsible for jaw opening, deviation, and anterior movement
The lateral pterygoid muscle is a two-headed, fan-shaped muscle located in the infratemporal fossa of the skull. 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 responsible for jaw opening, deviation, and anterior movement.
The lateral pterygoid muscle has a triangular shape with two heads: the superior and inferior. The superior head originates from the greater wing of the sphenoid, while the inferior head originates from the lateral pterygoid plate of the sphenoid. These two heads converge into a tendon, which attaches to the neck of the mandible. The lateral pterygoid muscle is supplied by a branch of the anterior division of the mandibular nerve, and its blood supply comes from the pterygoid branch of the second part of the maxillary artery.
The lateral pterygoid muscle contributes to the function of mastication by protruding and depressing the mandible when contracting bilaterally and rotating the mandible when contracting unilaterally. Bilateral contraction of the left and right lateral pterygoid muscles results in translation and rotation within both temporomandibular joints. The inferior heads pull the mandibular condyle anteriorly, causing the condyle to rotate against the inferior surface of the articular disc. Simultaneously, the superior heads pull the articular capsule and disc in the same direction to cushion the movements of the condyle. This results in the anterior translation of the disc and condyle, along with the rotation of the condyle, leading to the protrusion and depression of the mandible.
The lateral pterygoid muscle is also involved in side-to-side movements of the jaw. When the inferior head contracts unilaterally, it rotates the mandibular condyle anteromedially. This action occurs in conjunction with the contraction of the ipsilateral medial pterygoid muscle, swinging the jaw to the opposite side. Additionally, the lateral pterygoid muscle assists in jaw depression, along with the suprahyoid muscles, which attach the mandible to the hyoid bone. When the hyoid bone is fixed by the infrahyoid muscles, the suprahyoid muscles can lower the mandible.
Overall, the lateral pterygoid muscle plays a crucial role in jaw movements, including opening, deviation, and anterior translation and rotation, contributing to the essential functions of chewing and biting.
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The anterior digastric, mylohyoid, and inferior head of the lateral pterygoid are muscles that open the jaw
The mandible, or jawbone, is a powerful bone that requires a number of muscles to facilitate its movement. The movement of the jaw is called mastication, and the muscles that enable this are called the muscles of mastication. These muscles develop from the first pharyngeal arch and are therefore innervated by a branch of the trigeminal nerve, the mandibular nerve.
The masseter muscle is one of the four primary muscles of mastication. It is a powerful, superficial quadrangular muscle that is responsible for the elevation of the mandible, or jawbone, and some protraction of the mandible. It is also one of the muscles responsible for the action of mastication, or chewing. When the masseter contracts, it causes a powerful elevation of the mandible, closing the mouth. Its insertion along the angle and lateral surface of the ramus also allows it to aid in the protrusion of the mandible, allowing for the anterior motion of the jaw.
The lateral pterygoid muscle has a triangular shape with two heads: the superior and inferior. The inferior head of the lateral pterygoid is one of the muscles that open the jaw. The lateral pterygoid is the major protractor of the mandible, allowing for the depression of the chin and 'side to side' movement of the jaw. The lateral pterygoid is the only muscle to actively oppose the other muscles of mastication, allowing for the depression of the mandible.
The anterior digastric and mylohyoid are also muscles that open the jaw. These are accessory muscles of mastication, which are directly associated with mandibular function. They assist in jaw opening through their attachments to the hyoid bone, the mandible, and other bones.
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Accessory muscles that aid in jaw opening include the digastric, geniohyoid, and mylohyoid
The jaw, or mandible, is moved by the muscles of mastication. These muscles are associated with movements of the temporomandibular joint, which is the joint that connects the jaw to the skull. While the primary muscles of mastication are responsible for the majority of jaw movement, accessory muscles also play a role in jaw opening and closing. These accessory muscles include the digastric, geniohyoid, and mylohyoid muscles, collectively known as the suprahyoid muscles.
The digastric muscle has two parts: the anterior belly and the posterior belly. The anterior belly originates from the digastric fossa on the posterior surface of the mandible, while the posterior belly originates from the mastoid notch, a deep groove between the mastoid process and the styloid process of the temporal bone. Both parts of the muscle then insert on the body of the hyoid bone. Contraction of the digastric muscle causes the elevation of the hyoid bone or depression of the mandible, depending on whether the hyoid bone is fixed in place by the strap muscles.
The geniohyoid muscle originates from the mental spine of the mandible and inserts on the body of the hyoid bone. Contraction of this muscle results in the elevation and forward protrusion of the hyoid bone, along with depression of the mandible.
The mylohyoid muscle is a flat and triangular muscle that originates from the mandible near the molars. It inserts on the hyoid bone and plays a crucial role in swallowing and speaking. The mylohyoid muscle functions to elevate the hyoid bone and oral cavity, while depressing the mandible. These accessory muscles, therefore, provide essential support for the functions of mastication, deglutition, and articulation.
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Frequently asked questions
The lateral pterygoid muscle is responsible for opening the jaw.
The lateral pterygoid muscle has a triangular shape with two heads: superior and inferior.
The superior head originates from the greater wing of the sphenoid, while the inferior head originates from the lateral pterygoid plate of the sphenoid.
The lateral pterygoid muscle is responsible for the protraction of the mandible, allowing for the mouth to open. It also enables side-to-side movement of the jaw.
Yes, the masseter, temporalis, medial pterygoid, and superior head of the lateral pterygoid are involved in closing the jaw.
