Maximus Gage
The muscles of mastication are a group of muscles that control jaw movements, such as chewing, grinding, and mandibular depression. The four main muscles of mastication in humans are the masseter, temporalis, medial pterygoid, and lateral pterygoid. The lateral pterygoid muscle, in particular, plays a crucial role in depressing the mandible or lowering the jaw. This muscle has two heads or bellies, with the inferior belly being significantly larger than the superior belly. The origin of these bellies and their subsequent fusion into a tendon that attaches to the mandible contribute to its function in mandibular depression.
| Characteristics | Values |
|---|---|
| Muscle that depresses the lower jaw | Lateral pterygoid muscle |
| Other names | Inferior head of the lateral pterygoid, jaw depressor |
| Muscle structure | Triangular shape with two heads: superior and inferior |
| Muscle origin | The superior head originates from the greater wing of the sphenoid. The inferior head originates from the lateral surface of the lateral pterygoid plate of the sphenoid bone. |
| Muscle insertion | The fibres from both heads merge and insert onto a shallow depression on the anterior aspect of the neck of the mandible called the pterygoid fovea. |
| Innervation | Lateral pterygoid branch of the mandibular nerve |
| Vascularization | Pterygoid branches of the maxillary artery |
| Function | Depression of the mandible, protrusion, abduction, and mediotrusion |
| Role in jaw movement | Unilateral contraction results in lateral mandibular movement. Bilateral contraction results in protrusion and depression of the mandible. |
| Associated muscles | Masseter, temporalis, medial pterygoid, anterior digastric, mylohyoid, superior head of the lateral pterygoid |
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What You'll Learn
- The lateral pterygoid muscle is the only muscle that depresses the mandible
- The lateral pterygoid muscle has two heads or bellies
- The lateral pterygoid muscle has a triangular shape
- The muscles of mastication are divided into jaw-openers and jaw-closers
- The temporalis muscle originates from the temporal fossa
The lateral pterygoid muscle is the only muscle that depresses the mandible
The lateral pterygoid muscle is one of the four main muscles of mastication, which originate from the surface of the skull and attach to the rami of the mandible at the temporomandibular (TMJ) joint. The other three muscles are the masseter, temporalis, and medial pterygoid. These muscles enhance the process of eating and assist in grinding food. They also function to approximate the teeth. Three out of the four main muscles are responsible for adduction of the mandible, while one helps in the abduction of the mandible. The muscles of mastication are divided into jaw-openers (mandible depressors) and jaw-closers (mandible elevators).
The lateral pterygoid muscle has a triangular shape and is located in the infratemporal fossa. The muscle fibres converge inferiorly, forming a tendon that inserts into a depression called the pterygoid fovea on the neck of the condylar process 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 function of the lateral pterygoid depends on the degree of its contraction. Bilateral contraction of the lateral pterygoid muscles depresses the mandible, while unilateral contraction on one side, along with the ipsilateral medial pterygoid muscle, moves the mandible to the opposite side. This allows for side-to-side movements during chewing.
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The lateral pterygoid muscle has two heads or bellies
The lateral pterygoid muscle is a craniomandibular muscle that plays a crucial role in the inferior temporal region. It is one of the four muscles of mastication, along with the medial pterygoid, temporalis, and masseter muscles. All these muscles act upon the temporomandibular joint (TMJ) to enable chewing (mastication) and biting. The lateral pterygoid is the only muscle among the four that participates in depressing the mandible.
The two bellies of the lateral pterygoid muscle were always believed to have an antagonist action due to their different anterior insertions. However, the variations in the activity levels between the two bellies on each side determine the lateral and anteroposterior positioning of the jaw. The wide opening of the mandible may temporarily result in mandibular flexion, leading to distortion in the transverse plane. Thus, during impression-making of the lower arch, a widely open mouth may result in an inaccurate impression in the transverse dimension.
The lateral pterygoid muscle is innervated by the nerve to the lateral pterygoid muscle, a branch of the mandibular nerve (CN V3). There is one nerve for each head. The nerve to the superior head and the lateral half of the inferior head receives fibers from the buccal nerve, a branch of the mandibular nerve. Meanwhile, the nerve to the medial half of the inferior head gets fibers directly from the mandibular nerve. The vascular supply to the lateral pterygoid comes from the pterygoid branches of the maxillary artery and the ascending palatine branch of the facial artery.
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The lateral pterygoid muscle has a triangular shape
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. The lateral pterygoid muscle has a triangular shape with two heads: a superior head and an inferior head. The superior head is formed by the most superomedial fibres of the muscle, which originate from the infratemporal crest of the greater wing of the sphenoid bone. The superior head is much smaller than the inferior head. The inferior head, meanwhile, originates from the lateral surface of the lateral pterygoid plate of the sphenoid bone. The fibres from both heads converge to course posterolaterally in a predominantly horizontal plane.
The superior fibres insert into the anteromedial part of the articular capsule and articular disc of the temporomandibular joint. The inferior fibres insert into the pterygoid fovea on the neck of the condyloid process of the mandible. The superior attachment onto the temporomandibular joint allows the muscle head to act on the superior compartment of the joint, producing gliding motions of the disc and mandibular condyle. The lateral pterygoid muscle is innervated by the nerve to the lateral pterygoid muscle, a branch of the mandibular nerve (CN V3). It receives vascular supply from the pterygoid branches of the maxillary artery and the ascending palatine branch of the facial artery.
The lateral pterygoid muscle is the only muscle of mastication that causes depression of the mandible, or the lower jaw. It also assists with protrusion and side-to-side movement of the mandible. During unilateral contraction, the lateral pterygoid muscle moves the mandible medially. When both bellies of the lateral pterygoid muscle contract bilaterally, the mandible travels anteriorly (protrusion). The lateral pterygoid muscle plays a crucial role in controlling the function of the jaw and the temporomandibular joint.
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The muscles of mastication are divided into jaw-openers and jaw-closers
The muscles of mastication are a group of muscles that enable functions such as biting, chewing, and grinding. They attach to the mandible and produce movements of the lower jaw at the temporomandibular joint (TMJ). These movements include protrusion, retraction, elevation, depression, and side-to-side movement. The muscles of mastication can be divided into jaw-openers and jaw-closers.
The jaw-closing muscles, or jaw-closers, do most of the work associated with mastication. They include the masseter, temporalis, and pterygoid medialis. The masseter 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 major function of the masseter muscle is to elevate the mandible and approximate the teeth. The temporalis muscle is a large, flat muscle that lies within the temporal fossa of the skull. Its anterior vertical fibres oppose gravity to keep the mouth closed, while the posterior, more horizontal fibres produce a retraction of the mandible, pulling the jaw backwards. The pterygoid medialis assists the masseter and temporalis in elevating the mandible.
The jaw-opening muscles, or jaw-openers, include the lateral pterygoid and digastric muscles. The lateral pterygoid muscle is the only muscle of mastication that participates in depressing the mandible. It has two heads or bellies, with the inferior belly being three times larger than the superior belly. The lateral pterygoid muscle works together with the anterior belly of the digastric muscle and the mylohyoid muscle to open the mouth. When both bellies of the lateral pterygoid muscle contract bilaterally, the mandible moves forward (protrusion). The lateral pterygoid muscle also assists with protrusion and side-to-side movement of the mandible.
Neurophysiological evidence indicates that the RF substrate provides excitatory and inhibitory interneurons that are essential to the normal functions of the oromotor nuclei. Most of these premotor neurons are glutamatergic, while a smaller number are GABA-containing neurons. Three distinct classes of premototrigeminal interneurons have been identified: excitatory interneurons with projections to jaw-opener or jaw-closer motor neurons, and inhibitory interneurons with projections only to jaw-closer motor neurons. During the jaw-opening phase of mastication, jaw-closer motor neurons are under phasic glycinergic inhibition, allowing for a smoother and more rapid widening of the mandible.
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The temporalis muscle originates from the temporal fossa
The temporalis muscle, also known as the temporal muscle, is a masticatory muscle that facilitates the movement of the mandible at the temporomandibular joint. It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic arch. The origin point of the temporalis muscle spans the entire surface of the fossa below the temporal line, with some fibres also originating from the temporal fascia. This muscle is the strongest muscle of the temporomandibular joint and the primary retractor of the mandible.
The temporalis muscle is one of the four main muscles of mastication, which originate from the surface of the skull and attach onto the rami of the mandible at the temporomandibular joint. The other three muscles of mastication are the medial pterygoid, lateral pterygoid, and masseter. The lateral pterygoid muscle is the only muscle that participates in depressing the mandible. It is a craniomandibular muscle that plays a crucial role in the inferior temporal region and is active during mastication and mandibular movements.
The temporalis muscle is divided into anterior and posterior parts, with the anterior fibres running inferiorly in a vertical direction and the posterior fibres directed horizontally. The contraction of the posterior fibres of the muscle results in the backward movement of the mandible (retrusion), while the contraction of the anterior fibres moves the mandible dorsocranially (elevation). In unison, these actions facilitate the closing of the mouth and the approximation of the teeth. The unilateral contraction of the temporalis muscle also contributes to the side-to-side movements of the jaw.
The temporalis muscle receives its innervation from the anterior, middle, and posterior deep temporal branches of the anterior trunk of the mandibular nerve (V3). Its blood supply comes from the deep temporal branches of the maxillary artery and the middle temporal branches of the superficial temporal artery. Tension in the temporalis muscle can induce pain in the temporal area, and it is important to rule out inflammation of the superficial temporal artery, which runs in front of the ear along the zygomatic arch to the temporal area.
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Frequently asked questions
The lateral pterygoid muscle is the only muscle that participates in depressing the mandible.
The lateral pterygoid muscle is involved in protrusion (forward movement of the mandible) and mediotrusion (mandibular condyle movement towards the midline). It also assists with side-to-side movement of the jaw.
The muscles of mastication are a group of four muscles that are associated with movements of the jaw. These include the masseter, temporalis, medial pterygoid, and lateral pterygoid.
