A23 - Tempomandibular Joint Flashcards
what are the properties of a typical synovial joint?
- articular surfaces are lined by hyaline cartilage
- non-articular surfaces lines with synovial membrane
- capsule to enclose and retain fluid
- ligaments to strengthen joint
- skeletal muscles to move joint
What is the importance of the synovial membrane?
- contains fluid to nourish the articular surfaces
What does the synovial fluid do?
- reduces friction
- to cool the joint
- to remove waste products
What is the difference between the TMJ joint?
- all articular surfaces are FIBROUS
- temporal bone is covered in periosteum
- infra-articular disc is made of dense fibrous tissue
- head of mandibular condyle in perichondrium
- infra-articular disc is split into superior and inferior synovial cavities with their own synovial membrane
what makes up the TMJ?
- base of the temporal bone
- glenoid fossa of temporal bone
- head of the mandibular condyle
what is the function of the articular tubercle and where is it situated?
anterior to the glenoid fossa and prevents anterior dislocation
what is posterior to the glenoid fossa?
post-glenoid tubercle which prevents posterior disslocation
why is the post -glenoid tubercle less pronounced?
there are ligaments which also prevent dislocation
what is the function of the ptyergoid fovea?
where the lateral ptyergoid attaches and the disc is structurally connected to the ligament of this muscle
what is the key features of the condyle head?
- elongated latero-medially
- tilted anteriorly which helps it optimally articulate with the glenoid fossa
what is the joint capsule?
bandage that wraps around the joint to keep it complete, aiding stabilisation and keeps the synovial fluid in the joint
what ligament prevents posterior dislocation?
lateral temporomandibular ligament
what is the structure and function of the stylomandibular ligament?
- connects from the styloid process to the medial aspect of the angle of the mandible
- specialisation of the investing layer of deep cervical fascia surrounding the parotid gland
- weak ligament and restricts jaw openong
what is the importance and structure of the sphenomandibular ligament ?
- arises in the spine of the sphenoid and attached to the lingual
- main action is to prevent excessive jaw opening
what is the structure and function of the pterygomandibular raphe?
- extends from the hamulus of the pteygoid plate of the sphenoid down towards the retro-molar space
- role in attachment of other soft tissue including the buccinator muscle
what is the clinical relevance of the pterygomandibular raphe?
- used in the location of the inferior alveolar nerve block
- needle inserted in-between the coronoid notch and the pterygomandibular raphe
What is the importance of the intra-articular disc?
- merges with the joint capsule ensuring the separation of the joint into and upper and lower space
- provides stability of the joint during movement by ensuring a better fit between the mandible and the glenoid fossa
- contains dense fibrous connective tissue
- nerve receptors in the disc innervated by the auriculo-temporal nerve
What is the structure of the disc - anterior extension?
anterior extension - continuous with the joint capsule anteriorly and with the tendon of the lateral pteygoid
what is the process of initial jaw opening?
- anterior rotation of the head of condyle
- movemny occurs in the lower joint space
- disc remains in place
what is the process of full jaw opening?
- after initial opening the disc then translates anteriorly articulating with the mandibular fossa and articular eminence
- occurs in the upper joint space
what is the difference between internal derangement with reduction and without reduction?
- the disc gets stuck as the elastic fibre have become weakened
- with reduction it will return to its normal position itself without it needs clinical assistance
What causes dislocation of the TMJ’s ?
- occurs when the mandibular condyle becomes fixed in the anterosuperior aspect of the articular eminence
- spasm of the muscles of facial expression result in trismus, preventing the return of the condyle to the temporal fossa
describe the movement of the TMJ when the jaw opens
- bilateral and symmetrical depression
- initial anterior rotation
- subsequent anterior translation
- maximum normal opening > 3 fingersbreadth
describe the jaw closing movement of the TMJ
- bilateral and symmetrical depression
- initial posterior translation
- subsequent posterior rotation
describe lateral movements of the TMJ
- bilateral and asymmetrical
- working side lateral rotation/movement
- non-working slide anterior and medial rotation
describe the movement of the TMJ during protrusion and retrusion
protrusion - the mandible can be pulled forwards relative to the maxilla
retrusion - the mandible can be pulled backwards relative to the maxilla
what is the structure of the disc - posterior extension?
posterior extension - it is bilaminar. the superior head contains elastic fibres which pull the jaw to its resting position after opening . the inferior has a rich blood supply that fills with blood on opening, filling the space allowing good articulation and then empties on closing by draining into pterygeoid venous plexus
what is the structure of the disc - disc proper?
disc proper - form a doughnut shaped as it as a think anterior and posterior band and a thin intermediate zone
