Victor Forge
The muscles of mastication are a group of four muscles responsible for the movement of the jaw, which is also known as the mandible. These muscles include the masseter, temporalis, medial pterygoid, and lateral pterygoid. The lateral pterygoid muscle is the sole muscle of mastication that causes depression of the mandible, along with protrusion and side-to-side movement. The suprahyoid and infrahyoid muscles, also known as the strap muscles, also assist with the depression of the mandible.
| Characteristics | Values |
|---|---|
| Muscle that depresses the jaw | Lateral pterygoid muscle |
| Shape | Triangular |
| Number of heads | 2 |
| Origin of the upper head | Inferior temporal surface of the greater wing of the sphenoid bone |
| Origin of the lower head | Lateral aspect of the lateral pterygoid plate of the sphenoid bone |
| Function | Causes depression of the mandible, assists with protrusion and side-to-side movement of the mandible |
| Blood supply | Pterygoid branch of the second part of the maxillary artery |
| Innervation | Lateral pterygoid branch of the mandibular nerve |
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What You'll Learn
- The lateral pterygoid muscle is the primary muscle responsible for depressing the jaw
- The lateral pterygoid muscle has two parts: upper and lower
- The temporalis, medial pterygoid, lateral pterygoid, and masseter muscles are all muscles of mastication
- The muscles of mastication are responsible for the movement of the jaw
- The suprahyoid and infrahyoid muscles assist with depressing the mandible
The lateral pterygoid muscle is the primary muscle responsible for depressing the jaw
The lateral pterygoid muscle is a key muscle in the functioning of the jaw. It is one of the four muscles of mastication, which are responsible for the movement of the jaw, or mandible. The other three muscles of mastication are the masseter, temporalis, and medial pterygoid muscles. These muscles work together to enable the chewing motion of the mandible at the temporomandibular joint, assisting in grinding food and approximating the teeth.
The lateral pterygoid muscle has a unique triangular shape with two heads: the superior and inferior. The superior head originates from the greater wing of the sphenoid bone, while the inferior head originates from the lateral pterygoid plate of the sphenoid bone. The muscle fibres from these two heads converge inferiorly, forming a tendon that inserts into the neck of the mandible.
The lateral pterygoid muscle receives its innervation from the lateral pterygoid branch of the mandibular nerve, specifically the anterior division of the nerve. Its blood supply, or vascularization, is provided by the pterygoid branches of the maxillary artery. Understanding the anatomy of the lateral pterygoid muscle is crucial for comprehending the complex movements of the jaw and the overall function of the masticatory system.
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The lateral pterygoid muscle has two parts: upper and lower
The lateral pterygoid muscle is a craniomandibular muscle with two parts: an upper head and a lower head. 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 the only muscle among this group that participates in depressing the mandible and opening the jaw.
The upper head of the lateral pterygoid muscle originates on the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone. It inserts onto the articular disc and fibrous capsule of the temporomandibular joint. The lower head, on the other hand, originates on the lateral surface of the lateral pterygoid plate. It inserts onto the pterygoid fovea at the neck of the condyloid process of the mandible. The lower head is much wider than the upper head, and the two heads converge to form a tendon that attaches to the neck of the mandible.
The lateral pterygoid muscle is supplied by the pterygoid branches of the maxillary artery and the ascending palatine branch of the facial artery. It is innervated by the nerve to the lateral pterygoid muscle, a branch of the mandibular nerve (CN V3). The mandibular nerve also supplies the medial pterygoid muscle, which lies deep to the lateral pterygoid muscle. The lateral pterygoid muscle is involved in various mandibular movements, including protrusion, abduction (depression), and mediotrusion.
The lateral pterygoid muscle plays a significant role in maintaining the mandible's position. The variations in activity levels between the two heads determine the lateral and anteroposterior positioning of the jaw. The unilateral action of the lateral pterygoid muscle causes contralateral excursion, a form of mastication, and can move the mandible side to side. At the beginning of jaw depression, it is assisted by the digastric, mylohyoid, and geniohyoid muscles.
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The temporalis, medial pterygoid, lateral pterygoid, and masseter muscles are all muscles of mastication
The temporalis muscle is fan-shaped and originates from the temporal fossa, a shallow depression on the lateral aspect of the skull. It is covered by tough fascia, which can be harvested surgically and used to repair a perforated tympanic membrane. Its functions include elevation of the mandible (closing the mouth) and retraction of the mandible (moving the jaw posteriorly).
The medial pterygoid muscle is thick and rectangular with 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. The medial pterygoid muscle assists with elevation and protrusion of the mandible.
The lateral pterygoid muscle is triangular with two heads: superior and inferior. It has horizontally oriented muscle fibres, making it the major protractor of the mandible. The lateral pterygoid functions as the sole muscle of mastication that causes depression of the mandible, although this is largely the result of gravity. It also assists with protrusion and side-to-side movement of the mandible.
The masseter muscle is rectangular with three layers: superficial, deep, and intermediate. It is the most powerful muscle of mastication. The masseter muscle receives nerve input from the masseteric nerve, a division of the mandibular nerve.
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The muscles of mastication are responsible for the movement of the jaw
The muscles of mastication are a group of muscles responsible for the movement of the jaw. They enhance the process of eating by assisting in grinding food and bringing the teeth together. The four main muscles of mastication are the masseter, temporalis, medial pterygoid, and lateral pterygoid. These muscles attach to the rami of the mandible at the temporomandibular joint (TMJ) and function to move the jaw. The temporalis muscle is a fan-shaped muscle that originates from the temporal fossa of the skull and attaches to the coronoid process of the mandible. Its main function is to elevate the mandible and close the mouth, with its anterior vertical fibres opposing gravity to keep the mouth closed. The contraction of its posterior, more horizontal fibres produces a retraction of the mandible, pulling the jaw backwards. In addition, the temporalis muscle contributes to grinding movements by moving the mandible from side to side.
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, with the larger, superficial layer arising from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic arch. The masseter is the most powerful muscle of mastication.
The medial pterygoid muscle is a quadrangular muscle situated in the infratemporal fossa. It is composed of two heads that have 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 tuberosity of the maxilla. Both heads encircle the lower fibres of the lateral pterygoid muscle and insert on the medial surface of the mandibular ramus, close to the angle of the mandible. The medial pterygoid muscle is innervated by the medial pterygoid branch of the mandibular nerve.
The lateral pterygoid muscle is the primary muscle of the inferior temporal fossa and has two parts: an upper head and a lower head. The upper head originates from the inferior temporal surface of the greater wing of the sphenoid bone, while the lower head originates from the lateral aspect of the lateral pterygoid plate of the sphenoid bone. The lateral pterygoid muscle fibres converge to form a tendon that inserts into the pterygoid fovea of the neck of the condylar process of the mandible. This muscle functions as the sole muscle of mastication to cause depression of the mandible, although this movement is largely the result of gravity. It also assists with protrusion and side-to-side movement of the mandible.
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The suprahyoid and infrahyoid muscles assist with depressing the mandible
The jaw, or mandible, is a bone that can move and is controlled by several muscles. The suprahyoid and infrahyoid muscles are two groups of muscles that work together to control the position of the jaw. The infrahyoid muscles include the thyrohyoid, omohyoid, sternothyroid, and sternohyoid muscles. The suprahyoid muscles include the digastric, mylohyoid, geniohyoid, and stylohyoid muscles.
The suprahyoid and infrahyoid muscles work together to control the position of the hyoid bone and, consequently, the mandible. The infrahyoid muscles stabilise the hyoid bone, while the suprahyoid muscles pull the mandible open. When the hyoid bone is fixed, the suprahyoid muscles depress the mandible during the opening of the mouth. The infrahyoid muscles also work to control or limit the upward movement of the hyoid bone.
The suprahyoid muscles are frequently the focus of exercises designed to improve jaw strength. One such exercise involves the subject opening their jaw to its maximum capacity and maintaining this position for 10 seconds, with five repetitions in each set. This exercise has been shown to elevate the hyoid bone, which is beneficial for elderly individuals with a lower position of the hyoid bone at rest.
The suprahyoid and infrahyoid muscles act synergistically to assist with depressing the mandible. When the suprahyoid and infrahyoid muscles fix the hyoid bone, the mandible tends to be depressed.
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Frequently asked questions
The lateral pterygoid muscle is the primary muscle responsible for depressing the jaw.
The lateral pterygoid muscle is a triangular muscle that lies in the infratemporal fossa. It has two heads: superior and inferior.
The function of the lateral pterygoid muscle includes depressing the mandible, assisting with protrusion and side-to-side movement of the mandible.
The muscles of mastication are a group of four muscles associated with movements of the jaw. These are the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles.
