Rabu, 23 Mei 2012
Anatomy of the Temporomandibular(TMJ) joint
Anatomy of the Temporomandibular(TMJ) joint - TMJ is a synovial joint between condyle of the mandible an
mandibular fossa on the undersurface of the squamous part of the temporal bone.
The mandible is the single bone with the horizontal horse
shoe shaped body, which is continuous at its posterior ends with a pair of
vertical rami, each ramus is surmounted by a head or condyle.
The temporomandibular joint allows opening and closing the
mouth and complex chewing or side to side movements of the lower jaw.
The cranium with
which the mandible articulates, is also mechanically, a single componenet, with
a mandibular fossa on each side. This complex is in effective functioning
joint, as movement cannot take place at one temporomandibular joint, as
movement cannot take place at one TMJ without a concomitant movement occurring at
the joint on the opposite side.
The temporomandbular joints are thus the bilateral
components of a craniomandibular articulation.
The joint is separated into upper and lower joint cavities
by a fibrocartilagenous disc within it. Both bone surfaces are covered with a
layer of fibrocartilage identical with that of the disc. There is no hyaline
cartilage in the joint, so it is an atypical synovial joint.
The capsule is attached high p on the neck of the mandible
anteriorly, near the articular margin of the head, but lower down the neck posteriorly.
Above, it is attached anteriorly just in front of the articluar eminence of the
temporal bone,posteriorly to the squamotympanic fissure,and medially and
laterally to the margins of the mandibular fossa. It is lax above the disc, but
taut below. The synovial membrane lines the inside of the capsule and the
intracapsular posterior aspect of the neck of the mandible.
The articular disc attached around its periphery to the
inside of the capsule and to the medial and lateral poles of the head of the
mandible. Its upper surface is anteroposteriorly concavoconvex in the sagittal
plane to fit the articular eminence and fossa. The inferior surface is concave
in adaptation to the condyle. Anteriorly disc is continuous through its
capsular attachment with the tendon of lateral pterygoid.
Posteriorly disc divided
into two laminae. The upper fibroelastic lamina is attached to the margin of
the mandibular fossa. The lower non elastic fibrous lamina is attached to the
neck of the mandible. Between the two laminae is a pad of loosely textured
tissue continuing many blood vessels and sensory nerve endings. The disc has
two transverse thickened bands it is thinnest and relatively avascular.
Temporal ligament and sphenomandibular ligament reinforce
the capsule making it more strong.
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