Temporal mandibular joint (TMJ) Flashcards
what forms the temporomandibular joint?
formed by the articulation of the mandible and the temporal bone of the cranium
where is the TMJ located?
anteriorly to the tragus of the ear, on the lateral aspect of the face
what does the TMJ consist of?
articulations between three surfaces:
the mandibular fossa and articular tubercle (from the squamous part of the temporal bone), and the head of mandible
unique mechanism of TMJ?
the articular surfaces of the bones never come into contact with each other – they are separated by an articular disk
significance of presence of articular disk?
The presence of such a disk splits the joint into two synovial joint cavities, each lined by a synovial membrane
what covers the articular surface of the bones of TMJ?
covered by fibrocartilage, NOT hyaline cartilage
how many ligaments are there to support to TMJ?
three extracapsular ligaments
what are the 3 extracapsular ligaments stablising the TMJ?
Lateral ligament
Sphenomandibular ligament
Stylomandibular ligament
where does the lateral ligament run?
from the beginning of the articular tubule to the mandibular neck
what is the lateral ligament? function?
a thickening of the joint capsule, and acts to prevent posterior dislocation of the joint
where does the sphenomandibular ligament originate and attach to?
Originates from the sphenoid spine (spine of sphenoid bone), and attaches to the mandible
what is the stylomandibular ligmaent?
A thickening of the fascia of the parotid gland
function of the stylomandibular ligament?
Along with the facial muscles, it supports the weight of the jaw
what are movements of the TMJ produced by?
the muscles of mastication, and the hyoid muscles
how do the 2 divisions of the TMJ differ?
have different functions:
- Protrusion and Retraction
- Elevation and Depression
which part of the TMJ allows for protrusion and retraction?
The upper part of the joint allows protrusion and retraction of the mandible – the anterior and posterior movements of the jaw
which muscle is responsible for protrusion of the TMJ?
The lateral pterygoid muscle
assisted by the medial pterygoid
which muscle is responsible for retraction of the TMJ?
the geniohyoid and digastric muscles
function of lower part of TMJ?
permits elevation and depression of the mandible; opening and closing the mouth
what causes depression of the TMJ?
mostly caused by gravity
if there is resistance against depression, which muscles assist depression of TMJ?
digastric, geniohyoid, and mylohyoid muscles
what is elevation of TMJ caused by?
Elevation is very strong movement, caused by the contraction of the temporalis, masseter, and medial pterygoid muscles
arterial supply to TMJ?
provided by the branches of the EXTERNAL carotid, principally the superficial temporal branch
(contributing branches: the deep auricular, ascending pharyngeal and maxillary arteries)
what is the innervation to TMJ?
by the auriculotemporal and masseteric branches of the mandibular nerve (CN V3)
what can cause dislocation of the TMJ?
can occur via a blow to the side of the face, yawning, or taking a large bite
what happens in a dislocation of the TMJ?
The head of the mandible slips out of the manibular fossa, and is pulled anteriorly
how do patients with TMJ dislocation present?
unable to close their mouth
which nerves run close to TMJ?
The facial and auriculotemporal nerves run close to the joint, and can be damaged if the injury is traumatic
how do posterior dislocations of TMJ occur?
possible, but very rare:
requiring a large amount of force to overcome the postglenoid tubercle (holds neck of mandible) and strong intrinsic lateral ligament
what can arthritis of the TMJ cause?
can cause inflammation of the temporomandibular joint
what do patients with arthritis of TMJ complain of?
jaw pain, stiffness and joint ‘grating’
