Logan Steele
The mandible, or lower jaw, is connected to the skull via the temporomandibular joint, which allows for movement in all planes. The muscles of mastication are a group of muscles that control the movement of the mandible. They originate on the skull and insert into the mandible, allowing for jaw movements during contraction. The four main muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. While the masseter muscle is responsible for elevating the mandible, the lateral pterygoid muscle is the sole muscle that causes depression or lowering of the mandible.
| Characteristics | Values |
|---|---|
| Muscles responsible for lowering the mandible | Lateral pterygoid, geniohyoid, mylohyoid, and digastric muscles |
| Location | Lateral pterygoid muscle has a triangular shape with two heads: superior and inferior. The medial pterygoid muscle is thick and rectangular with a superficial and deep head. The masseter muscle is strong, thick, and rectangular with a superficial and deep part. |
| Function | The lateral pterygoid muscle is the sole muscle responsible for depressing the mandible. The geniohyoid, mylohyoid, and digastric muscles help in opening the jaw. The masseter muscle elevates the mandible and assists in protrusion and retraction. |
| Innervation | The lateral pterygoid muscle is innervated by the mandibular division of the trigeminal nerve. The masseter muscle is innervated by the masseteric nerve, a branch of the mandibular nerve. |
| Blood Supply | The lateral pterygoid muscle's blood supply is not clear. The masseter muscle's blood supply is from the masseteric artery, a branch of the maxillary artery. |
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What You'll Learn
- The lateral pterygoid muscle is the only muscle that causes depression of the mandible
- The masseter muscle elevates the mandible
- The temporalis muscle also elevates the mandible
- The geniohyoid, mylohyoid, and digastric muscles are responsible for opening the jaw
- The medial pterygoid muscle has a quadrangular shape and two heads
The lateral pterygoid muscle is the only muscle that causes depression of the mandible
The mandible, or lower jaw, is connected to the temporal bone of the skull via the temporomandibular joint (TMJ). The TMJ is an extremely complex joint that permits movement in all planes. The muscles of mastication attach to the rami of the mandible and function to move the jaw. The four main muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. These muscles originate from the surface of the skull and attach onto the rami of the mandible at the TMJ.
The temporalis muscle is a fan-shaped muscle with anterior fibres that have a vertical orientation, mid fibres that have an oblique orientation, and posterior fibres that have a more horizontal orientation. The origin of the temporalis muscle spans 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 masseter muscle is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. It is composed of two layers that differ slightly in their attachments. The larger, superficial layer arises from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic arch. The deep layer of the masseter muscle arises from the medial surface and inferior margin of the zygomatic arch. The masseter muscle functions to elevate the mandible, with a minor contribution to protrusion of the mandible.
The medial pterygoid muscle is a thick, quadrangular muscle with a superficial head and a deep head. The superficial head of the medial pterygoid originates from the maxillary tuberosity of the inferior maxilla, while the deep head originates from the medial aspect of the lateral pterygoid plate of the sphenoid bone. Both heads attach to the ramus of the mandible near the angle of the mandible and function to elevate the mandible.
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The masseter muscle elevates the mandible
The masseter muscle is one of the four muscles of mastication, or chewing. It is a strong, quadrangular muscle with two layers: a superficial layer and a deep layer. The superficial layer is larger and arises from the maxillary process of the zygomatic bone, while the deep layer arises from the medial surface and inferior margin of the zygomatic arch.
The masseter muscle is responsible for elevating the mandible, or jaw, causing a powerful jaw closure. This elevation is a result of the contraction of the superior part of the muscle, which runs diagonally to the front, moving the mandible forward in a protrusion movement. In addition to its role in jaw closure, the masseter muscle also assists in stabilizing the tension of the articular capsule of the temporomandibular joint.
The masseter muscle works in conjunction with other muscles of mastication, including the temporalis, medial pterygoid, and lateral pterygoid muscles. These muscles attach to the mandible and enable movements such as chewing and grinding food. The temporalis muscle, for example, also contributes to elevating the mandible, while the lateral pterygoid muscle is the sole muscle responsible for depressing, or lowering, the mandible.
The masseter muscle is innervated by the masseteric nerve, a branch of the mandibular nerve. Its blood supply is derived from the masseteric artery, a branch of the maxillary artery. The masseter muscle is a vital component of the masticatory system, facilitating essential functions such as chewing and maintaining oral health.
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The temporalis muscle also elevates the mandible
The mandible, or lower jaw, is connected to the temporal bone of the skull via the temporomandibular joint. This joint is extremely complex and permits movement in all planes. The muscles of mastication, which are responsible for the chewing movement of the mandible, originate on the skull and attach to the mandible, allowing for jaw movements during contraction.
The temporalis muscle is one of the four classical muscles of mastication. It is a fan-shaped muscle with anterior fibres that have a vertical orientation, mid fibres that have an oblique orientation, and posterior fibres that have a horizontal orientation. The origin of the temporalis muscle spans 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 function of the anterior and mid fibres of the temporalis muscle is to elevate the mandible. The posterior fibres of the temporalis muscle function to retract the mandible. The temporalis muscle is also involved in side-to-side grinding movements.
The other three classical muscles of mastication are the masseter, medial pterygoid, and lateral pterygoid muscles. 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: a larger, superficial layer that arises from the maxillary process of the zygomatic bone and an anterior two-thirds of the zygomatic arch; and a deep layer that arises from the medial surface and inferior margin of the zygomatic arch. The medial pterygoid muscle is a thick, rectangular muscle with a superficial head and a deep head. The lateral pterygoid muscle is the sole muscle of mastication that causes depression of the mandible, although this is largely the result of gravity.
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The geniohyoid, mylohyoid, and digastric muscles are responsible for opening the jaw
The human mandible, or lower jaw, is connected to the skull via the temporomandibular joint (TMJ). This joint is extremely complex, allowing movement in all planes. The muscles of mastication originate on the skull and insert into the mandible, enabling jaw movement during contraction.
The primary muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. These muscles are responsible for the chewing movement of the mandible at the TMJ, enhancing the process of eating and assisting in grinding food. They also function to approximate the teeth.
While the muscles mentioned above are responsible for closing the jaw, other muscles are involved in opening it. Specifically, the geniohyoid, mylohyoid, and digastric muscles are responsible for this action. These muscles, along with the masseter, are part of the suprahyoid muscle group.
The masseter muscle is a strong, rectangular muscle that covers the lateral aspect of the ramus of the mandible. It is composed of two layers: a superficial layer and a deep layer. The superficial layer arises from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic arch. The deep layer arises from the medial surface and inferior margin of the zygomatic arch. These layers converge to form tendon insertions on the outer surface of the mandibular ramus and the coronoid process of the mandible. The masseter functions to elevate the mandible, approximate the teeth, and assist in retracting and protruding the mandible.
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The medial pterygoid muscle has a quadrangular shape and two heads
The medial pterygoid muscle is a thick quadrangular muscle with a superficial head and a deep head. It is one of the four muscles of mastication, along with the lateral pterygoid, masseter, and temporalis muscles. These muscles are responsible for the movement of the mandible at the temporomandibular joint, which is essential for chewing food.
The medial pterygoid muscle has two main functions: depressing the mandible and protruding the mandible. This muscle helps in lowering the mandible, especially when the maxillary and mandibular teeth are close together. The depression of the mandible is also facilitated by the lateral pterygoid muscle, which is the sole muscle of mastication responsible for this movement.
The medial pterygoid muscle arises from two heads with different origins. The larger deep head originates from the medial surface of the lateral pterygoid plate of the sphenoid bone and the pyramidal process of the palatine bone. The smaller superficial head originates from the maxillary tuberosity and the grooved surface of the pyramidal process of the palatine bone.
From their respective origins, the muscle fibres of the two heads descend posteroinferiorly and laterally, surrounding the lower fibres of the lateral pterygoid muscle. The deep head forms the bulk of the muscle, while the superficial head contributes to the closure of the jaw. Together, the two heads of the medial pterygoid muscle insert onto the triangular impression located on the medial surface of the mandible.
The medial pterygoid muscle is innervated by the medial pterygoid branch of the mandibular nerve (CN V3), which is a branch of the trigeminal nerve (CN V). It receives its blood supply from the pterygoid branches of the maxillary artery. The medial pterygoid muscle works in coordination with other muscles of mastication to produce a range of mandibular movements, including elevation, depression, protrusion, retraction, and side-to-side grinding motions.
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Frequently asked questions
The muscles of mastication are a group of muscles responsible for the chewing movement of the mandible at the temporomandibular (TMJ) joint. The four main muscles of mastication are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles.
The lateral pterygoid muscle is the sole muscle of mastication that causes depression of the mandible.
The lateral pterygoid muscle also assists with protrusion and side-to-side movement of the mandible.
The muscles of mastication enhance the process of eating and assist in grinding food. They also function to approximate the teeth.
