TMJ – NORMAL ANATOMY PPT
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The Temporomandibular joint (TMJ)
The Temporomandibular joint (TMJ) is composed of the temporal bone and the mandible, as well as a specialized dense fibrous structure, the articular disk, several ligaments, and numerous associated muscles.
Also called as craniomandibular joint / articulation.
TMJ is diarthrodial ( which is a discontinuous articulation of bones permitting freedom of movement )
It is also a synovial joint, lined on its inner aspect by a synovial membrane, which secretes synovial fluid. The fluid acts as a joint lubricant and supplies the metabolic and nutritional needs of the nonvascularized internal joint structures.
The TMJ is a compound joint, composed of four articulating surfaces:
the articular facets of the temporal bone and of the mandibular condyle and the superior and inferior surfaces of the articular disk.
TMJ CORONAL VIEW
Mandibular (glenoid) fossa
Limits :- anteriorly, the articular eminence
posteriorly, a small conical post
Articular eminence :- small prominence on the zygomatic arch. Strongly convex anteroposteriorly n somewhat concave mediolaterally.
Post glenoid tubercle :- separates fossa laterally from tympanic plate n tympanic plate separates the TMJ from the bony part of the external auditory canal.
Glenoid fossa :- lined by a dense avascular fibrocartilage n in crosssection the fossa n eminence form a hazy ‘s’ posteroanteriorly.
Mandibular condyle :-
broad laterally n narrow medially.
Mediolaterally – bt. 13 to 25 mm
Anteroposteriorly – bt. 5.5 to 16 mm
N.T.-The articular part of condyle is covered by fibrocartilagenous tissue n not with hyaline cartilage, as in most joints of the human body
SOFT TISSUE ANATOMY
CAPSULAR LIGAMENT (LATERAL VIEW)
It encompasses each joint, attaching superiorly to the temporal bone along the border of the mandibular fossa and eminence and inferiorly to the neck of the condyle along the edge of the articular facet.
It surrounds the joint spaces and the disk, attaching anteriorly and posteriorly as well as medially and laterally, where it blends with the collateral ligaments.
FUNCTION of the capsular ligament is to resist medial, lateral, and inferior forces, thereby holding the joint together. It offers resistance to movement of the joint only in the extreme range of motion.
A secondary function of the capsular ligament is to contain the synovial fluid within the superior and inferior joint spaces
Synovial fluid is considered an ultrafiltrate of plasma. It contains a high concentration of hyaluronic acid, which is thought to be responsible for the fluid’s high viscosity.
The proteins found in synovial fluid are identical to plasma proteins.
Alkaline phosphatase, which may also be present in synovial fluid, is thought to be produced by chondrocytes.
Leukocytes are also found in synovial fluid.
Only a small amount of synovial fluid, usually less than 2 mL, is present within the healthy TMJ.
Functions of the synovial fluid include lubrication of the joint, phagocytosis of particulate debris, and nourishment of the articular cartilage.
Sphenomandibular ligament :- it is a flate band arising from the spine of sphenoid & the petrotympanic fissure,runs downward n medially to the TMJ capsule n gets inserted on the lingula of the mandible.
Remnant of meckle’s cartilage.
N.T :- maxillary artery n auriculotemporal nerve lies bt. It n mandubular neck.
The stylomandibular ligament :- it is dense thick band of deep cervical facia extending from the styloid process to the mandibular angle.
Articular disc ( meniscus )
Composed of dense fibrous connective tissue and is nonvascularized and noninnervated.
Anatomically the disk can be divided into three general regions as viewed from the lateral perspective:
The anterior band
the central intermediate zone, and
the posterior band.
TMJ LATERAL VIEW
It promotes lubrication , energy absorption n joint range of motion.
It acts as shock absorber enabling the articulating bones to move against each other with minimum friction n heat production.
Disc has very little potential for repair after insult.
Branches from Superficial
temporal & Maxillary Artery
& Masseteric Nerve
TMJ PATHOLOGY , PATIENT’S HISTORY
Age – Younger-MPDS common
Older degenerative disease common
Higher class people
H/O pain – MPDS – dull & morning time
TMJ pain – Sharp & increased
Jaw & joints symptoms
Oral habit : Bruxism
Medical history : Rheumatoid arthritis
H/O : Headache
Family history : Rheumatoid arthritis
Trans orbital view or antero-posterior view.
Trans cranial or lateral view.
Adv. It provide superior osseous anatomical images
without any superimposition than conventional x-
ray.And in different plane.
It is good for hard tissue.
Disadv. Can’t asses dynamic depiction of soft tissue
( MRI )
Adv. – Doesn’t use ionising radiation.
excellent for soft tissue
Disadv. – very expensive
Defect in position or structure of the joint disc & its attachment can be determined using arthrography.
arthrography is performed by injecting the contrast madia in to the joint space and after it radiograph is taken.
Category: Oral Anatomy