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Encyclopedia > Temporomandibular joint
Temporomandibular joint
Articulation of the mandible. Lateral aspect.
Our friend here suffers from "too much jaw."
Latin articulatio temporomandibularis
Gray's subject #75 297
Artery superficial temporal artery
MeSH Temporomandibular+Joint
Dorlands/Elsevier a_64/12161641

The temporomandibular joint (From the Latin for "too much jaw") is a diarthrodial joint that connects the condyle of the mandible (lower jaw) to the temporal bone at the side of a skull. As a modified hinge joint, not only does the TMJ enable the jaw to rotate open and closed, it also enables the jaw to translate forward and backward. The condyle can also move laterally and medially. Image File history File links Gray309. ... Image File history File linksMetadata TMJ.JPG‎ our friend has too much jaw File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Section of an artery For other uses, see Artery (disambiguation). ... Arteries of the neck - right side. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Elseviers logo. ... A joint (from French joint) (articulation) is the location at which two bones make contact (articulate). ... The condyloid process is thicker than the coronoid, and consists of two portions: the condyle, and the constricted portion which supports it, the neck. ... It has been suggested that this article or section be merged with jaw. ... Human jaw front view Human jaw left view Human jaw top view The jaw is either of the two opposable structures forming, or near the entrance to, the mouth. ... The temporal bones (os temporales) are situated at the sides and base of the skull. ... It has been suggested that temporal fenestra be merged into this article or section. ...


Some erroneously refer to pain in the temporomandibular joint as TMJ, when in fact, TMJ is really the name of the joint. Pain in this joint in actually called TMD, or temporomandibular joint disorder. Temporomandibular joint disorder (TMJD or TMD), or TMJ syndrome, is an acute or chronic inflammation of the temporomandibular joint, which connects the lower jaw to the skull. ...

Contents

Articulation

The TMJ is a ginglymoarthrodial joint, referring to its dual compartment structure and function (ginglymo- and arthrodial). A joint is the location at which two bones make contact. ... A gliding joint (arthrodial joint, plane articulation) is a joint which admits of only gliding movement; it is formed by the apposition of plane surfaces, or one slightly concave, the other slightly convex, the amountf,dkdgnnnflkrbballriinnfbvaklermmdbhhsmmfkIt is the form present in the joints between the articular processes of the vertebrae...


The condyle articulates with the temporal bone in the glenoid fossa. The glenoid fossa is a concave depression in the squamous portion of the temporal bone. The squama of the temporal bone forms the anterior and upper part of the bone, and is scale-like, thin, and translucent. ...


However, these two bones are actually separated by an articular disc, a concept of structure unknown throughout the rest of the body. Diagrammatic section of a diarthrodial joint, with an articular disk. ...


This disc divides the TMJ into two distinct compartments. The inferior compartment allows for pure rotation of the condylar head, which corresponds to the first 20 mm or so of the opening of the mouth. After the mouth is open to this extent, the mouth can no longer open without the superior compartment of the TMJ becoming active.


At this point, if the mouth continues to open, not only is the condylar head rotating within the lower compartment of the TMJ, but the entire apparatus (condylar head and articular disc) translates, or slides, forward in the glenoid fossa and down the articular eminance of the temporal bone, thus incorporating an anterior movement into the further opening of the mouth. This can be demonstrated by placing a resistance fist against the chin and trying to open the mouth more than 20 or so mm.


Components

There are six main components of the TMJ.

  • Mandibular condyles
  • Articular surface of the temporal bone
  • Capsule
  • Articular disc
  • Ligaments
  • Lateral pterygoid

The lateral pterygoid (or external pterygoid) is a muscle of mastication with two heads. ...

Capsule and articular disc

The capsule is a fibrous membrane that surrounds the joint and incorporates the articular eminance. It attaches to the articular eminance, the articular disc and the neck of the mandibular condyle.


The articular disc functions as articular surfaces against both the temporal bone and the condyles and divides the joint into two sections, as described in more detail below. It is biconcave in structure and attaches to the condyle medially and laterally. The anterior portion of the disc splits in the vertical dimension, coincident with the insertion of the superior head of the lateral pterygoid. The posterior portion also splits in the vertical dimension, and the area between the split continues posteriorly and is referred to as the retrodiscal tissue. Unlike the disc itself, this piece of connective tissue is vascular and innervated, and in some cases of anterior disc displacement, the pain felt during movement of the mandible is due to the condyle pressing on this area.


Ligaments

There are three ligaments associated with the TMJ: one major and two minor ligaments.

  • The major ligament, the temporomandibular ligament, is really the thickened lateral portion of the capsule, and it has two parts: an outer oblique portion (OOP) and an inner horizontal portion (IHP).

These ligaments are important in that they define the border movements, or in other words, the farthest extents of movements, of the mandible. However, movements of the mandible made past the extents functionally allowed by the muscular attachments will result in painful stimuli, and thus, movements past these more limited borders are rarely achieved in normal function. The temporomandibular ligament (external lateral ligament) consists of two short, narrow fasciculi, one in front of the other, attached, above, to the lateral surface of the zygomatic arch and to the tubercle on its lower border; below, to the lateral surface and posterior border of the neck of the mandible. ... The stylomandibular ligament is a specialized band of the cervical fascia, which extends from near the apex of the styloid process of the temporal bone to the angle and posterior border of the ramus of the mandible, between the Masseter and Pterygoideus internus. ... The parotid gland is the largest of the salivary glands. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... At the junction of the lower border of the ramus of the mandible with the posterior border is the angle of the mandible, which may be either inverted or everted and is marked by rough, oblique ridges on each side, for the attachment of the Masseter laterally, and the Pterygoideus... The sphenomandibular ligament (internal lateral ligament) is a flat, thin band which is attached above to the spina angularis of the sphenoid bone, and, becoming broader as it descends, is fixed to the lingula of the mandibular foramen. ... The great wings, or ali-sphenoids, are two strong processes of bone, which arise from the sides of the body, and are curved upward, lateralward, and backward; the posterior part of each projects as a triangular process which fits into the angle between the squama and the petrous portion of...


Innervation and vascularization

The nerves of the temporomandibular joint are derived from the auriculotemporal and masseteric branches of the mandibular nerve, and the arteries from the superficial temporal branch of the external carotid artery. The auriculotemporal nerve is a branch of the mandibular nerve that runs with the superficial temporal artery and vein, and provides sensory innervation to various regions on the side of the head. ... The Masseteric Artery is small and passes lateralward through the mandibular notch to the deep surface of the Masseter. ... The mandibular nerve is the third branch (V3) of the trigeminal nerve. ... Superficial temporal redirects here. ... The carotid artery is a major artery of the head and neck. ...


The specific mechanics of proprioception in the temporomandibular joint involve four receptors. Ruffini endings function as static mechanoreceptors which deal with the posture of the mandible. Pacinian corpuscles are dynamic mechanoreceptors which accelerate movement during reflexes. Golgi tendon organs function as static mechanoreceptors for protection of ligaments around the temporomandibular joint. Free nerve endings are the pain receptors for protection of the temporomandibular joint itself. Ruffini Endings are one of the four main cutaneous mechanoreceptors. ... A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. ... A Pacinian corpuscle is a structure that functions as a mechanoreceptor. ... Organ of Golgi (neurotendinous spindle) from the human tendo calcaneus. ... NERVE ENDINGS SUCK PENIS!!! ...

Sagittal section of the articulation of the mandible.
Sagittal section of the articulation of the mandible.

In order to faciliate proper function, there is neither innervation nor vascularization within the central portion of the articular disc. Had there been any nerve fibers or blood vessels, a person would bleed everytime he or she moved his or her jaw; however, he or she would never actually move his or her jaw, because it would be too painful. Image File history File links Gray311. ... Image File history File links Gray311. ...


Jaw movements

During jaw movements, only the mandible moves.


Normal movements of the mandible during function, such as mastication, or chewing, are known as excursions. There are two lateral excursions (left and right) and the forward excursion, known as protrusion. The reversal of protrusion is retrusion. Mastication or chewing is the process by which food is torn and/or crushed by teeth. ...


When the mandible is moved into protrusion, the mandibular incisors, or front teeth of the mandible, are moved so that they first come edge to edge with the maxillary (upper) incisors and then surpass them, producing a temporary underbite. This is accomplished by translation of the condyle down the articular eminance (in the upper portion of the TMJ) without any more than the slightest amount of rotation taking place (in the lower portion of the TMJ), other than that necessary to allow the mandibular incisors to come in front of the maxillary incisors without running into them. (This is all assuming an ideal Class I or Class II occlusion, which is not entirely important to the lay reader.) Incisors are the first kind of tooth in heterodont mammals. ...


During chewing, the mandible moves in a specific manner as delineated by the two TMJs. The side of the mandible that moves laterally is referred to as either the working or rotating side, while the other side is referred to as either the balancing or orbiting side. The latter terms, although a bit outdated, are actually more precise, as they define the sides by the movements of the respective condyles.


When the mandible is moved into a lateral excursion, the working side condyle (the condyle on th side of the mandible that moves outwards) only performs rotation (in the horizontal plane), while the balancing side condyle performs translation. During actual functional chewing, when the teeth are not only moved side to side, but also up and down when biting of the teeth is incorporated as well, rotation (in a vertical plane) also plays a part in both condyles.


The mandible is moved primary by the four muscles of mastication: the masseter, medial pterygoid, lateral pterygoid and the temporalis. These four muscles, all innervated by V3, or the mandibular division of the trigeminal nerve, work in different groups to move the mandible in different directions. Contraction of the lateral pterygoid acts to pull the disc and condyle forward within the glenoid fossa and down the articular eminance; thus, action of this muslce serves to open the mouth. The other three muscles close the mouth; the masseter and the medial pterygoid by pulling up the angle of the mandible and the temporalis by pulling up on the coronoid process. In human anatomy, the masseter is one of the muscles of mastication. ... Medial pterygoid can refer to: Medial pterygoid muscle Medial pterygoid plate Category: ... The temporalis muscle is one of the muscles of mastication. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the middle ear), and other muscles in the floor of the mouth, such as the... (ramus mandibulæ; perpendicular portion) The ramus of the mandible is quadrilateral in shape, and has two surfaces, four borders, and two processes. ...


Disorders

See Temporomandibular joint disorder for more details

The most common disorder of the TMJ is disc displacement. In essence, this is when the articular disc, attached anteriorly to the superior head of the lateral pteygoid muscle and posteriorly to the retrodiscal tissue, moves out from between the condyle and the fossa, so that the mandible and temporal bone contact is made on something other than the articular disc. This, as explained above, is usually very painful, because unlike these adjacent tissues, the central portion of the disc contains no sensory innervation. Temporomandibular joint disorder (TMJD or TMD), or TMJ syndrome, is an acute or chronic inflammation of the temporomandibular joint, which connects the lower jaw to the skull. ...


In most instances of disorder, the disc is displaced anteriorly upon translation, or the anterior and inferior sliding motion of the condyle forward within the fossa and down the articular eminance. On opening, a "pop" or "click" can sometimes be heard and usually felt as well, indicating the condyle is moving back onto the disk, known as "reducing the joint". Upon closing, the condyle will slide off the back of the disc, hence another "click" or "pop". Now the condyle is posterior to the disc. Upon clenching, the condyle is compressing the bilaminar area, and the nerves, arteries and veins against the temporal fossa. When the disc stays anterior to the condylar head upon closing, this is termed disc displacement without reduction.


TMJ pain is generally due to one of three reasons.

  • The most common cause of TMJ pain is myofascial pain dysfunction syndrome, primarily involving the muscles of mastication.
  • Internal derangements is defined as an abnormal relationship of the disc to any of the other components of the TMJ. Disc displacement is an example of internal derangement.
  • Degenerative joint disease, otherwise known as osteoarthritis is the organic degeneration of the articular surfaces within the TMJ.

Osteoarthritis (OA, also known as degenerative arthritis or degenerative joint disease, and sometimes referred to as arthrosis or osteoarthrosis or in more colloquial terms wear and tear), is a condition in which low-grade inflammation results in pain in the joints, caused by wearing of the cartilage that covers and...

See also


  Results from FactBites:
 
Temporomandibular joint Summary (1174 words)
The temporomandibular joint (TMJ) is a diarthrosis joint that connects the mandible (lower jaw) to the temporal bone at the side of a skull.
This disorder is marked by an acute or chronic inflammation of the temporomandibular joint.
The nerves of the temporomandibular joint are derived from the auriculotemporal and masseteric branches of the mandibular nerve, the arteries from the superficial temporal branch of the external carotid.
Temporomandibular joint - Wikipedia, the free encyclopedia (805 words)
The temporomandibular joint (TMJ) is a diarthrosis joint that connects the mandible (lower jaw) to the temporal bone at the side of a skull.
This disorder is marked by an acute or chronic inflammation of the temporomandibular joint.
The nerves of the temporomandibular joint are derived from the auriculotemporal and masseteric branches of the mandibular nerve, the arteries from the superficial temporal branch of the external carotid.
  More results at FactBites »

 
 

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