A23 - Tempomandibular Joint

Question 1

what are the properties of a typical synovial joint?

Answer 1

• 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

Question 2

What is the importance of the synovial membrane?

Answer 2

• contains fluid to nourish the articular surfaces

Question 3

What does the synovial fluid do?

Answer 3

• reduces friction
• to cool the joint
• to remove waste products

Question 4

What is the difference between the TMJ joint?

Answer 4

• 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

Question 5

what makes up the TMJ?

Answer 5

• base of the temporal bone
• glenoid fossa of temporal bone
• head of the mandibular condyle

Question 6

what is the function of the articular tubercle and where is it situated?

Answer 6

anterior to the glenoid fossa and prevents anterior dislocation

Question 7

what is posterior to the glenoid fossa?

Answer 7

post-glenoid tubercle which prevents posterior disslocation

Question 8

why is the post -glenoid tubercle less pronounced?

Answer 8

there are ligaments which also prevent dislocation

Question 9

what is the function of the ptyergoid fovea?

Answer 9

where the lateral ptyergoid attaches and the disc is structurally connected to the ligament of this muscle

Question 10

what is the key features of the condyle head?

Answer 10

• elongated latero-medially

- tilted anteriorly which helps it optimally articulate with the glenoid fossa

Question 11

what is the joint capsule?

Answer 11

bandage that wraps around the joint to keep it complete, aiding stabilisation and keeps the synovial fluid in the joint

Question 12

what ligament prevents posterior dislocation?

Answer 12

lateral temporomandibular ligament

Question 13

what is the structure and function of the stylomandibular ligament?

Answer 13

• 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

Question 14

what is the importance and structure of the sphenomandibular ligament ?

Answer 14

• arises in the spine of the sphenoid and attached to the lingual
• main action is to prevent excessive jaw opening

Question 15

what is the structure and function of the pterygomandibular raphe?

Answer 15

• 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

Question 16

what is the clinical relevance of the pterygomandibular raphe?

Answer 16

• used in the location of the inferior alveolar nerve block

- needle inserted in-between the coronoid notch and the pterygomandibular raphe

Question 17

What is the importance of the intra-articular disc?

Answer 17

• 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

Question 18

What is the structure of the disc - anterior extension?

Answer 18

anterior extension - continuous with the joint capsule anteriorly and with the tendon of the lateral pteygoid

Question 19

what is the process of initial jaw opening?

Answer 19

• anterior rotation of the head of condyle
• movemny occurs in the lower joint space
• disc remains in place

Question 20

what is the process of full jaw opening?

Answer 20

• after initial opening the disc then translates anteriorly articulating with the mandibular fossa and articular eminence
• occurs in the upper joint space

Question 21

what is the difference between internal derangement with reduction and without reduction?

Answer 21

• 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

Question 22

What causes dislocation of the TMJ’s ?

Answer 22

• 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

Question 23

describe the movement of the TMJ when the jaw opens

Answer 23

• bilateral and symmetrical depression
• initial anterior rotation
• subsequent anterior translation
• maximum normal opening > 3 fingersbreadth

Question 24

describe the jaw closing movement of the TMJ

Answer 24

• bilateral and symmetrical depression
• initial posterior translation
• subsequent posterior rotation

Question 25

describe lateral movements of the TMJ

Answer 25

- bilateral and asymmetrical - working side lateral rotation/movement - non-working slide anterior and medial rotation

Question 26

describe the movement of the TMJ during protrusion and retrusion

Answer 26

protrusion - the mandible can be pulled forwards relative to the maxilla retrusion - the mandible can be pulled backwards relative to the maxilla

Question 27

what is the structure of the disc - posterior extension?

Answer 27

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

Question 28

what is the structure of the disc - disc proper?

Answer 28

disc proper - form a doughnut shaped as it as a think anterior and posterior band and a thin intermediate zone