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The mandible is the largest and strongest bone in the human face, forming the lower jaw and holding the lower teeth in place. The muscles of mastication are a group of muscles that enable the movement of the mandible, or jaw, at the temporomandibular joint (TMJ). These muscles are responsible for chewing, grinding food, and closing the mouth. The four main muscles of mastication are the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles.
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What You'll Learn
- The mandible is the largest and strongest bone of the face
- The muscles of mastication are a group of four muscles that control jaw movement
- The masseter muscle is the most powerful muscle of mastication
- The temporalis muscle is fan-shaped and fills the temporal fossa
- The medial pterygoid muscle is thick and rectangular with two heads
The mandible is the largest and strongest bone of the face
The mandible, or the lower jaw, is the largest and strongest bone in the human face. It is composed of a curved, horseshoe-shaped body that holds the teeth, and a pair of rami that project upwards to form the temporomandibular joint. The mandible is formed by the fusion of two separate bones during the first year of life. This fusion results in a strong, single bone that acts as the receptacle for the lower teeth.
The mandible is essential for several critical functions, including chewing, speaking, and facial aesthetics. It provides structural support to the lower face and helps maintain the shape and integrity of the jaw. The bone also serves as an attachment site for several muscles, including the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles, which are collectively known as the muscles of mastication. These muscles enable a range of mandibular movements, including elevation, depression, protrusion, retraction, and side-to-side grinding motions that assist in chewing and grinding food.
The masseter muscle, the most powerful muscle of mastication, has a rectangular shape with three layers: superficial, deep, and intermediate. It originates from the zygomatic arch and attaches to the ramus of the mandible. The function of the masseter is to elevate the mandible, closing the mouth, and assisting in approximating the teeth.
The temporalis muscle, on the other hand, is fan-shaped and fills the temporal fossa. Its fibres converge to form a tendon that inserts on the coronoid process of the mandible. The anterior and mid fibres of the temporalis muscle elevate the mandible, while the posterior fibres contribute to retraction and side-to-side grinding movements.
The medial pterygoid muscle, located inferiorly to the lateral pterygoid, has a rectangular shape with two heads: deep and superficial. The deep head is larger than the superficial head. The medial pterygoid muscle fibres converge to form a tendon that inserts on the medial ramus of the mandible, assisting with elevation, protrusion, and side-to-side grinding motions.
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The muscles of mastication are a group of four muscles that control jaw movement
The masseter muscle is the most powerful muscle of mastication. It is quadrangular in shape and has two parts: deep and superficial. It lies superficial to the pterygoids and temporalis muscles. The masseter originates from the inferior zygomatic arch and the anterior two-thirds of the zygomatic arch, with a connection to the posterior aspect of the zygomatic bone. The main function of the masseter is to elevate the mandible and approximate the teeth.
The temporalis muscle is fan-shaped and fills the temporal fossa. It originates from the temporal fossa to the inferior temporal line of the lateral skull. The function of the anterior and mid fibres of the temporalis muscle is to elevate the mandible, while the posterior fibres function to retract the mandible. The temporalis muscle also contributes to grinding movements by moving the mandible from side to side.
The medial pterygoid muscle is rectangular with a superficial head and a deep head. The deep head is larger and originates from the medial surface of the lateral pterygoid plate of the sphenoid bone, while the superficial head originates from the maxillary tuberosity of the inferior maxilla. The medial pterygoid muscle assists with elevation and protrusion of the mandible, as well as side-to-side movement.
The lateral pterygoid muscle is the primary muscle of the inferior temporal fossa and has two parts: an upper and lower head. It functions as the sole muscle of mastication to cause depression of the mandible, as well as assisting with protrusion and side-to-side movement. The function of the lateral pterygoid depends on the degree of its contraction, with bilateral contraction causing protrusion and depression of the mandible, and unilateral contraction moving the mandible to the opposite side.
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The masseter muscle is the most powerful muscle of mastication
The mandible is the lower jaw, and the muscles that enable its movement are the muscles of mastication. There are four muscles of mastication: the masseter, temporalis, medial pterygoid, and lateral pterygoid. These muscles are responsible for the chewing movement of the mandible at the temporomandibular joint (TMJ). They enhance the process of eating by assisting in grinding food, and they also function to approximate the teeth.
The major function of the masseter muscle is to elevate the mandible, approximate the teeth, and assist in chewing. The intermediate and deep muscle fibres of the masseter function to retract the mandible, while the superficial fibres function to protrude the mandible. The deep fibres are important stabilisers of the TMJ. The masseter muscle works in conjunction with two other jaw-closing muscles, the temporalis and the medial pterygoid, to close the jaw.
The temporalis muscle is fan-shaped and fills the temporal fossa. It originates from the temporal fossa to the inferior temporal line of the lateral skull. The temporalis muscle fibres converge inferiorly, forming a tendon that exits the temporal fossa, passing underneath the zygomatic arch, and inserting on the coronoid process of the mandible. The temporalis muscle is supplied by the deep temporal nerve, a branch of the anterior division of the mandibular nerve. Its blood supply is derived from the deep temporal part of the maxillary artery and the middle temporal branches of the superficial temporal artery. The function of the anterior and mid fibres of the temporalis muscle is to elevate the mandible, while the posterior fibres function to retract the mandible.
The medial pterygoid muscle is thick and rectangular, with a superficial head and a deep head. The superficial head originates from the maxillary tuberosity of the inferior maxilla, while the deep head originates from the medial surface of the lateral pterygoid plate of the sphenoid bone. The medial pterygoid muscle fibres converge inferiorly, forming a tendon that inserts on the medial ramus of the mandible. The medial pterygoid muscle assists with elevation and protrusion of the mandible, and it also helps with side-to-side mandibular motion for grinding food.
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The temporalis muscle is fan-shaped and fills the temporal fossa
The mandible is the lower jawbone. The muscles of mastication are a group of muscles associated with movements of the jaw. There are four muscles of mastication: the masseter, temporalis, medial pterygoid, and lateral pterygoid.
The temporalis muscle is a powerful muscle of the temporomandibular joint. It can be divided into two functional parts: the anterior and posterior. The anterior portion runs vertically and its contraction results in the elevation of the mandible (closing the mouth). The contraction of its anterior fibres moves the mandible dorsocranially (elevation). The posterior portion has fibres that run horizontally, and contraction of this portion results in the retrusion of the mandible. The contraction of its posterior fibres pulls the mandible posteriorly (retrusion). In unison, these actions facilitate the closing of the mouth and the approximation of the teeth.
The temporalis muscle is also known as the temporal muscle. It is a broad, fan-shaped convergent muscle on each side of the head. The muscle is covered by tough fascia, which can be harvested surgically and used to repair a perforated tympanic membrane. The temporalis muscle is the strongest muscle of the temporomandibular joint and the primary retractor of the mandible.
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The medial pterygoid muscle is thick and rectangular with two heads
The mandible is the bone that forms the lower jaw. The medial pterygoid muscle is one of the four muscles of mastication, or chewing, that produce movements of the mandible at the temporomandibular joint. The other three muscles are the masseter, temporalis, and lateral pterygoid muscles.
The two heads of the medial pterygoid muscle converge to form a tendon that inserts on the medial ramus of the mandible, creating an axis for a strong pull of this bone. The medial pterygoid muscle fibres insert onto a triangular impression located on the medial surface of the mandible. The fibres attach via a strong tendinous lamina that extends from the inferior alveolar (or mandibular) foramen superiorly, to the mylohyoid groove anteroinferiorly.
The medial pterygoid muscle has several functions, including elevating the mandible (closing the mouth), protruding the mandible, mastication (especially when the maxillary and mandibular teeth are close together), and excursing the mandible (contralateral excursion occurs with unilateral contraction). The medial pterygoid muscle assists with the side-to-side movement of the mandible, helping to grind food.
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Frequently asked questions
The muscles of mastication are a group of muscles responsible for the movement of the jaw. They include the temporalis, masseter, medial pterygoid, and lateral pterygoid muscles.
The mandible muscles enable functions such as chewing and grinding food by moving the jaw (mandible) through protrusion, retraction, elevation, depression, and side-to-side movements.
The temporalis muscle is fan-shaped, while the masseter muscle is rectangular or quadrangular in shape. The medial pterygoid muscle is thick and rectangular, and the lateral pterygoid muscle is triangular.
The temporalis muscle is located in the temporal fossa of the skull, the masseter muscle is in the cheek area, and the medial and lateral pterygoids are in the infratemporal fossa.
Unlike most facial muscles, the mandible muscles are innervated by the trigeminal nerve (CN V), specifically the mandibular branch (CN V3). The mandibular nerve is both sensory and motor.
