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The temporomandibular joint (TMJ) is a unique joint that connects the jaw to the skull. It is the only joint in the body that requires both left and right joints to cause a movement and involves two separate movements: a hinge movement and a translational movement. The TMJ is formed by the articulation of the mandible and the temporal bone of the cranium and is located in front of the ear on the lateral aspect of the face. The TMJ is a common source of pain, which is usually due to muscle pain or myofascial pain, discomfort, or pain in the muscles that control the jaw, neck, and shoulder function. Several muscles attach to the TMJ and control its movement, including the temporalis, masseter, medial pterygoid, digastric, geniohyoid, and mylohyoid muscles.
| Characteristics | Values |
|---|---|
| Description | The TMJ is a synovial, condylar and hinge-type joint that connects the jaw to the skull |
| Location | Found anteriorly to the tragus of the ear, on the lateral aspects of the face |
| Function | Allows opening, closing, and side-to-side movement of the mouth |
| Muscles Involved | Temporalis, Masseter, Medial Pterygoid, Digastric, Geniohyoid, Mylohyoid, Lateral Pterygoid |
| Nerve Innervation | Mandibular nerve (CN V3), Facial nerve (CN VII), C1, C2, C3 |
| Blood Supply | Branches of the external carotid, including the superficial temporal branch, deep auricular, ascending pharyngeal, and maxillary arteries |
| Disorders | Temporomandibular Disorder (TMD), including myofascial pain, internal derangement, degenerative joint disease, and growth disturbances |
| Treatment | Physiotherapy, conservative methods, Botox |
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What You'll Learn
The sternal head of the sternocleidomastoid muscle
The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. It is a two-headed neck muscle with attachments to the manubrium of the sternum (sternal head) and the clavicle (clavicular head). The sternal head of the sternocleidomastoid muscle is a round fasciculus, tendinous in the front and fleshy behind. It arises from the upper part of the front of the manubrium sterni and travels superiorly, laterally, and posteriorly.
The two heads of the sternocleidomastoid muscle join into one muscle belly that inserts on the lateral surface of the mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone. The muscle is closely related to certain neurovascular structures that pass through the neck and is innervated by the accessory nerve.
The sternocleidomastoid muscle is a lateral neck flexor and is involved in various complex physiological movements beyond this principal function. A unilateral contraction of the muscle flexes the cervical vertebral column to the same side and rotates the head to the opposite side. A bilateral contraction elevates the head by dorsally extending the upper cervical joints, while also flexing the lower cervical column, causing an overall bending of the neck towards the chest.
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Digastric, geniohyoid, and mylohyoid muscles
The digastric, geniohyoid, and mylohyoid muscles are all part of the suprahyoid group of muscles, which are located superior to the hyoid bone and form the floor of the mouth. The digastric muscle is a small, paired muscle in the anterior compartment of the neck. It is comprised of two parts: the anterior and posterior bellies, which have different embryological origins and innervations. The anterior belly is derived from the first pharyngeal arch and is innervated by the nerve to the mylohyoid muscle, a branch of the inferior alveolar nerve that arises from the mandibular nerve. The posterior belly, on the other hand, is derived from the mesoderm of the second pharyngeal arch and is innervated by the digastric branch of the facial nerve (cranial nerve 7). The anterior belly receives its arterial blood supply from the submental artery of the facial artery, while the posterior belly is supplied by the occipital and posterior auricular arteries.
The geniohyoid muscle is a short, triangular structure located beneath the genioglossus muscle and above the digastric and mylohyoid muscles. It moves the hyoid bone upward and forward, widening the airway passage. The geniohyoid receives its nerve supply from the first cervical nerve roots that run within the hypoglossal nerve. It is also supplied by branches of the lingual artery.
The mylohyoid muscle is a broad, triangular-shaped muscle that forms the floor of the oral cavity and supports the floor of the mouth. It originates from the mylohyoid line of the mandible and attaches to the hyoid bone. The mylohyoid elevates the hyoid bone, the floor of the mouth, and the tongue, playing a role in deglutition and speech. It receives its nerve supply from the mylohyoid nerve, a branch of the inferior alveolar nerve, which arises from the mandibular nerve. The mylohyoid is also supplied by the submental branch of the facial artery and the mylohyoid branch of the inferior alveolar artery.
Together, these three muscles contribute to mandibular depression, facilitating a wide opening of the mouth. They also assist in neck flexion and swallowing.
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Temporalis, masseter, and medial pterygoid muscles
The temporalis, masseter, and medial pterygoid muscles are all involved in the movement of the temporomandibular joint (TMJ). The TMJ is a unique joint that connects the jaw to the skull and facilitates a wide range of movements, including opening, closing, and side-to-side movements of the mouth.
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. It is covered by a tough fascia and plays a crucial role in elevating the mandible, resulting in the closing of the mouth. Additionally, the temporalis muscle contributes to the retraction of the mandible, moving the jaw backward.
The masseter muscle, a strong quadrangular muscle, covers the lateral aspect of the ramus of the mandible. It consists of two layers with slightly different attachments. The superficial layer arises from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic arch. The deep layer, on the other hand, originates from the medial surface and inferior margin of the zygomatic arch. The masseter muscle assists in elevating the mandible and also contributes to the protrusion or protraction of the mandible, moving it forward.
The medial pterygoid muscle has a quadrangular shape and is composed of two heads: the deep head and the superficial head. The 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 superficial head originates from the tuberosity of the maxilla. The medial pterygoid muscle works together with other muscles to enable various movements of the mandible, including elevation, depression, protrusion, and rotation.
These three muscles, along with the lateral pterygoid muscle, comprise the muscles of mastication. They attach to the mandible and coordinate their contractions to produce movements of the lower jaw at the TMJ, such as chewing and grinding. The proper functioning of these muscles is essential for maintaining the health and stability of the TMJ, as any dysfunction or disorder in this area can lead to severe pain and limitations in an individual's daily life.
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Muscles that control jaw, neck and shoulder function
The temporomandibular joint (TMJ) is formed by the articulation of the mandible and the temporal bone of the cranium. It allows for the opening, closing, and side-to-side movement of the mouth. The TMJ is located in front of the ear, on the lateral aspect of the face. The TMJ is a unique joint, as it requires both left and right joints to facilitate movement, and it involves two separate movements: a hinge movement and a translational movement.
The muscles that control the TMJ are innervated by the mandibular nerve, the facial nerve, and C1, C2, and C3. These muscles work together to perform various movements, such as mandibular depression, elevation, lateral deviation, retrusion, and protrusion. For example, the masseter muscle is responsible for the elevation of the mandible, causing the mouth to close. It originates from the zygomatic arch and inserts along the angle and lateral surface of the mandibular ramus. The lateral pterygoid muscle, on the other hand, allows for the depression of the mandible and the opening of the mouth.
The neck muscles support and stabilise the head, neck, and upper spine, and they assist in chewing, swallowing, and breathing. There are about 30 neck muscles, which are skeletal muscles attached to bones by tendons. They are voluntary muscles, allowing for control over their movement. Neck muscles are found at the front, sides, and back of the neck, extending from the base of the skull and jaw down to the shoulder blades and collarbone.
The sternal head of the sternocleidomastoid muscle, or SCM, is a neck muscle that turns the head side to side. It can refer pain in front of and behind the ear, as well as to other areas of the head and face.
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Muscles that control chewing, swallowing, and speech
The temporomandibular joint (TMJ) connects the jaw to the skull. It is formed by the articulation of the mandible and the temporal bone of the cranium. The TMJ allows for the opening, closing, and side-to-side movement of the mouth.
Muscles that Control Chewing
The muscles involved in chewing (also known as muscles of mastication) include the lateral pterygoid, masseter, medial pterygoid, and temporalis. The lateral pterygoid is a fan-shaped muscle that helps the jaw open, while the masseter, medial pterygoid, and temporalis muscles aid in closing the jaw. These muscles work together to enable the various movements of the TMJ, including mandibular depression, elevation, lateral deviation, retrusion, and protrusion.
Muscles that Control Swallowing
Swallowing is a complex process that involves the coordination of the brain, nerves, and muscles. While the brain initiates the swallowing reflex, it is the muscles that physically perform the act of swallowing. The specific muscles involved in swallowing include the digastric, geniohyoid, and mylohyoid muscles, which assist in the depression of the mandible during swallowing.
Muscles that Control Speech
Facial muscles are essential for speech production, as they enable the articulation of sounds and the formation of words. There are about 20 facial muscles that work together to control movements involved in speech, including the buccinator muscle in the cheek and the depressor anguli oris and depressor labii inferioris muscles in the chin and lower lip, respectively. These muscles contract and relax in specific sequences to produce the precise movements necessary for speech.
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Frequently asked questions
The temporomandibular joint (TMJ) is formed by the articulation of the mandible and the temporal bone of the cranium. It allows opening, closing, and side-to-side movement of the mouth.
The muscles that act on the TMJ are innervated by the mandibular nerve (CN V), the facial nerve (CN VII), C 1, C 2, and C 3. The TMJ is also associated with the sternal head of the sternocleidomastoid muscle (SCM), which can refer pain to the front and behind the ear, the forehead, cheek, chin, eye, under the jaw, and into the breastbone.
TMD refers to a group of conditions involving the orofacial region, affecting either the masticatory muscles or the TMJ. Symptoms include pain in the TMJ, restriction of mandibular movement, and TMJ sounds such as clicking and crepitations.
