Logan Steele
The human face has about 20 facial muscles that enable us to chew and make facial expressions. The jaw muscles are involved in the complex functions of chewing, swallowing, and speaking. The four main muscles of mastication (chewing food) are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. These muscles attach to the rami of the mandible, which is the technical name for the bone that makes up the lower part of our jaw, and help to move the jaw. The temporalis muscle, for example, is a fan-shaped muscle that helps the jaw close, while the lateral pterygoid is a fan-shaped muscle that helps the jaw open.
| Characteristics | Values |
|---|---|
| Number of facial muscles | 20 |
| Functions | Chewing, making facial expressions, swallowing, speaking |
| Types of muscles of mastication | Lateral pterygoid, Masseter, Medial pterygoid, Temporalis |
| Masseter muscle characteristics | Most superficial of jaw muscles, two sections (superficial and deep), contracts to elevate mandible and close mouth |
| Temporalis muscle characteristics | Fan-shaped, assists in elevating mandible and closing mouth |
| Medial pterygoid muscle characteristics | Two heads (deep and superficial), assists in elevating mandible and protrusion of jaw |
| Lateral pterygoid muscle characteristics | Two heads, can function bilaterally or unilaterally, assists in depressing, protrusion, and side-to-side movement of mandible |
| Common issues | Myofascial pain, myalgia, myospasm, bruxism, TMJ dysfunction, trauma, infection |
Explore related products
Masseter muscle
The masseter is a powerful muscle that runs from the cheek to the side of the jaw and helps the jaw close. It is one of the muscles of mastication, which are the facial muscles involved in chewing. The masseter is the most superficial of the jaw muscles, but it has two sections: a superficial portion and a deeper part. The masseter muscle is innervated by the masseteric nerve, a branch of the mandibular nerve, which is a branch of the trigeminal nerve. The masseter receives its blood supply from the masseteric artery, a branch of the maxillary artery.
The masseter muscle is a paired, strong, thick, and rectangular muscle that originates from the zygomatic arch and extends down to the mandibular angle. The zygomatic bone is a large bone on the sides of the skull. The masseter has two divisions: a superficial portion and a deep portion. 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 deep portion of the masseter muscle originates from the entire surface of the zygomatic arch.
The masseter muscle is involved in the elevation and protrusion of the mandible, which is the technical name for the lower part of the jaw. When the masseter contracts, it causes a powerful elevation of the mandible, causing the mouth to close. The masseter muscle also helps to stabilise the tension of the articular capsule of the temporomandibular joint. The temporomandibular joint is the joint that connects the mandible to the skull.
The masseter muscle can become enlarged in patients who habitually clench or grind their teeth, a condition known as bruxism. This masseteric hypertrophy is usually asymptomatic and soft, and it is usually bilateral but can be unilateral. Singers often experience various kinds of masseter tension, which is often treated with transdermal massages or stretches as a vocal warm-up.
Relieving Tension in Your Neck: Targeting the Scalenes
You may want to see also
Explore related products
Lateral pterygoid
The lateral pterygoid 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 specifically helps to protrude and depress the mandible when contracting bilaterally and rotate the mandible when contracting unilaterally.
The lateral pterygoid muscle is supplied by the lateral pterygoid nerve, a branch of the mandibular nerve (CN V3), which is itself a branch of the trigeminal nerve (CN V). The muscle is innervated by muscular branches from the anterior division of the mandibular nerve. In some variations, it may also be innervated by the deep temporal nerves, the masseteric nerve, and the buccal nerve. The lateral pterygoid muscle is supplied by pterygoid branches of the maxillary artery, which passes through the split between the superior and inferior heads of the muscle.
The lateral pterygoid has two heads, the superior (upper) and inferior (lower), with the inferior head being much wider and larger than the superior 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 inferior head originates from the lateral surface of the lateral pterygoid plate of the sphenoid bone. 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, while the inferior fibres insert into the pterygoid fovea on the neck of the condyloid process of the mandible.
The lateral pterygoid muscle contributes to chewing and biting functions by protruding and depressing the mandible when contracting bilaterally. When contracting unilaterally, it rotates the mandible, creating a side-to-side movement of the jaw. Unlike the other muscles of mastication, the lateral pterygoid is the only muscle that can assist in depressing the mandible (opening the jaw) independently. Dysfunction of this muscle may contribute to temporomandibular disorders.
Hand Muscles: The Intricate Flexors and Extensors
You may want to see also
Explore related products
Medial pterygoid
The medial pterygoid muscle is a thick, quadrilateral-shaped muscle that is located in the infratemporal fossa, behind the masseter and temporalis muscles. It is one of the muscles of mastication, or chewing, and is involved in several functions related to jaw movement.
The medial pterygoid has two heads: a deep head and a superficial head. The deep head is larger and arises from the medial surface of the lateral pterygoid plate of the sphenoid bone and the pyramidal process of the palatine bone. The superficial head is smaller and arises from the maxillary tuberosity and the grooved surface of the pyramidal process of the palatine bone. The fibres from both heads converge and insert onto the triangular impression found on the medial surface of the ramus and angle of the mandible, or the lower jaw.
The medial pterygoid muscle is innervated by the medial pterygoid nerve, a branch of the mandibular nerve, which is itself a branch of the trigeminal nerve. It receives its vascular supply primarily from the pterygoid and buccal branches of the maxillary artery, with contributions from the ascending palatine artery and muscular branches of the facial artery. In some cases, the medial pterygoid may also receive vascular supply from a direct branch of the external carotid artery.
The medial pterygoid has several functions, including elevating the mandible (closing the mouth), protruding the mandible, and assisting in mastication, particularly when the upper and lower teeth are close together. Unilateral contraction of the medial pterygoid causes a slight medial rotation of the mandible, while bilateral contraction results in the elevation and protrusion of the mandible. Additionally, the medial pterygoid works together with the lateral pterygoid muscle to create side-to-side movement of the jaw.
Unlocking Hip Muscle Power: Why It's Important
You may want to see also
Explore related products
Temporalis
The temporalis is a fan-shaped muscle that is one of the four primary muscles involved in mastication (chewing). It is a powerful muscle of the temporomandibular joint and is the primary retractor of the mandible. The temporalis muscle can be divided into two functional parts: the anterior and the posterior. The anterior portion runs vertically, and its contraction results in the elevation of the mandible (closing the mouth). The posterior portion has fibres that run horizontally, and contraction of this portion results in retrusion of the mandible. The middle portion, with fibres running in an oblique direction, is used for both elevation and retraction of the mandible. The unilateral contraction of the temporalis muscle is important for side-to-side movements of the jaw.
The temporalis muscle is covered by the temporal fascia, also known as the temporal aponeurosis. This fascia is commonly used in tympanoplasty, the surgical reconstruction of the eardrum. The temporalis muscle is accessible on the temples and can be seen and felt contracting while the jaw is clenching and unclenching. The muscle receives its blood supply from the deep temporal branches of the maxillary artery and middle temporal branches of the superficial temporal artery. The auriculotemporal, facial and zygomaticotemporal nerves run across the superficial aspect of the temporalis muscle.
Tension of the temporalis muscle can induce pain in the temporal area. This can be caused by nocturnal bruxism, the habitual grinding of teeth while sleeping, and clenching of the jaw while stressed. This can lead to overwork of the temporalis muscle, resulting in pain and even myotendinous rupture during a seizure due to extreme clenching of the jaw.
The temporalis muscle may be used in reconstructive surgery of the mouth. During pterional craniotomy, incisions are chosen based on the ease of reattaching the temporalis muscle after the bone fragment is replaced.
Accessory Muscles: Understanding Their Unique Supportive Role
You may want to see also
Explore related products
Jaw muscle disorders
The face has about 20 facial muscles, including the jaw muscles, that work together to control the parts of our face. These muscles are essential for chewing, making facial expressions, and performing other complex functions like swallowing and speaking. The masseter is the most superficial of the jaw muscles, while the medial and lateral pterygoids are found deeper. The temporalis and masseter muscles are responsible for closing the jaw, while the lateral pterygoid helps the jaw open.
One common jaw muscle disorder is bruxism, which involves involuntary teeth clenching or grinding. This disorder can occur during sleep or while awake and can lead to tooth wear, destruction of periodontal structures, and tension-type headaches. Bruxism can be a cause or a result of TMJ dysfunction, creating an imbalance in the forces within the muscles of mastication.
Other jaw muscle disorders include masticatory myofascial pain, characterised by a dull ache with trigger points that produce referred pain, and myositis, an inflammatory condition of the muscles caused by trauma or infection, resulting in swelling, redness, and increased temperature in the affected area. In addition, myofibrotic contracture can cause painless shortening of the jaw muscles due to fibrosis, leading to limited mouth opening and resistance to passive jaw muscle stretch.
Treatment for jaw muscle disorders depends on the underlying cause and severity of symptoms. Non-invasive options such as medication and nonsurgical treatments are usually tried first, including pain relievers, anti-inflammatory drugs, muscle relaxers, and antidepressants. If symptoms persist, jaw surgery may be recommended. Healthcare providers may also suggest jaw exercises, quitting gum-chewing or nail-biting habits, and using a plastic bite guard to address teeth grinding.
The Core of Postural Muscles: Understanding the Fundamentals
You may want to see also
Frequently asked questions
The jaw has four main muscles of mastication (chewing food): the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles.
The temporalis muscle is fan-shaped and engages in the elevation of the mandible (closing the mouth) and retracting the mandible (pulling the lower jaw in).
The masseter muscle is the most superficial of the jaw muscles and is responsible for the elevation of the mandible (closing the mouth) and the protrusion and retraction of the mandible (aiding chewing).
Some common issues with the jaw muscles include myofascial pain, masticatory myalgia, myospasm, bruxism, and temporomandibular joint (TMJ) dysfunction.
