ANATOMY - TMJ

Question 1

what are the muscles of mastication?

Answer 1

masseter
temporalis
lateral pterygoid
medial pterygoid

Question 2

what is the masseter responsible for?

Answer 2

• elevation of the mandible
• protrude the mandible

Question 3

roles of the temporalis

Answer 3

• anterior fibres elevate mandible
• posterior fibres retract mandible

Question 4

2 components of the lateral pteryoid

Answer 4

• superior head
• inferior head

Question 5

what is the role of the superior lateral pteryoid?

Answer 5

pull the capsule and disc forward during mouth opening

stabilises condyle during chewing

Question 6

what is the role of the inferior lateral pteryoid?

Answer 6

depresses and protrude mandible
allows rotation of mandible

Question 7

where is the medial pteryoid

Answer 7

sits deep to the masseter

Question 8

role of the medial pteryoid?

Answer 8

• elevates the mandible

Question 9

what bone do the muscles of mastication attach to? describe the different bones and where they are

Answer 9

sphenoid bone

Question 10

describe the sphenoid bone and its components

Answer 10

Question 11

what bone does the lateral pytergoid attach to?

Answer 11

sphenoid bone:

• lateral surface of lateral plate
• greater wing

Question 12

what bone does the medial pytergoid attach to?

Answer 12

sphenoid bone:
-posterior surface of lateral plate

Question 13

what is the structure of the TMJ?

Answer 13

the condyle of the mandible
- sits in mandibular fossa
- of temporal bone

• the joint capsule allows it to be synovial - keeps fluid in
• articular disc - allow movement without bone on bone contact
• articular tubercule - bony growth pushes the disc

Question 14

what separates the TMJ into superior and inferior cavities?

Answer 14

articulator disc

• mandibular fossa
• articulator disc
• condyle

Question 15

how can the TMJ move?

Answer 15

rotate
depress
elevate
protrusion
retraction
translational - everything moves at the same time

Question 16

what movement happens within the inferior TMJ cavity?

Answer 16

rotation

Question 17

what movement happens within the superior TMJ cavity?

Answer 17

protrusion-retraction movements
translation

Question 18

which ligaments support the TMJ?

Answer 18

• joint capsule - contains synovial fluid and articular disc
• lateral ligament - ‘TMJ ligament’

accessory ligaments
- sphenomandibular ligament
- stylomandibular ligament

Question 19

where does the joint capsule attach?

Answer 19

from temporal region superior and neck of mandible inferior ally

Question 20

describe the lateral ligament

Answer 20

has two parts
- inner horizontal fibres
- super oblique fibres

Question 21

what are the roles of the inner horizontal fibres - lateral ligament of TMJ?

Answer 21

• prevent excessive posterior displacement
• stops crushing of vascular tissue posterior to mandible

Question 22

are the inner horizontal fibres - lateral ligament strong?

Answer 22

the neck would litttterally break before these fibressss jheeze

Question 23

what are the roles of the outer oblique fibres - lateral ligament of TMJ.

Answer 23

• pushes the condyle as mouth opens onto articular tubercle
• limited stretch - prevent over-rotation

Question 24

what is the articular tubercule also known as?

Answer 24

articular eminence

Question 25

describe where they connect and the role of the accessory ligaments - sphenomandibular ligament (SML) and stylomandibular ligament (STML)

Answer 25

SML: - from sphenoid to mandible - support role of outer oblique fibres - prevent excessive inferior displacement STML: - from styloid process to posterior ramus of mandible - unclear function - may limit excessive protrusion

Question 26

role of the articular disc.

Question 27

structure of the articular disc

Answer 27

1. anterior capsular ligament - part of the joint capsule 2. superior retrodiscal lamina - posterior and superior of the disc - elastic - to push disc forward 3. inferior retrodiscal lamina - posterior and inferior of the disc - not elastic 4. retrodiscal tissue - highly vascular - just posterior to disc - essential to joint integrity 5. lateral and medial discal ligaments - keep the disc close to the condyle 6. superior and inferior articular cavity - superior is larger

Question 28

how does the articulator disc move when opening and closing the mouth? 9 steps

Answer 28

1. at rest - mandibular fossa, disc and condyle in close proximity 2. lateral pteryoid - inferior head - rotates mandible anterior 3. disc pushes anteriorly towards articular tubercle 4. lateral pteryoid - superior head relaxed 5. mandibular head resting on articular tubercle 6. superior retrodiscal lamina - pulls disc posterior during closing - until all elastic tension removed 7. lateral pterygoid - superior head - contracts to slow down anterior posterior movements 8. lateral pterygoid - inferior head relaxed 9. disc back into place and in rest mode

Question 29

how can the articulator disc be involved in temporomandibular clicking?

Answer 29

1. disc is sat anterior - mandible is seated posterior to it 2. normal movements 3. mandible head snaps onto the articular disc - instead of moving with it 4. normal movements back 5. disc is still left forward 6. mandible head clicks off the disc posteriorly

Question 30

why does jaw locking happen?

Answer 30

loss of retrodiscal tissue elasticity pulling the disc back into place 1. disc is already sat anterior 2. mandible is posterior 3. disc goes beyond articular eminence 4. mandible head does not snap back into correct position 5. opening of mouth is restricted there are no normal phases

Question 31

define myotactic

Answer 31

the reflex contraction of a muscle when an attached tendon is pulled

Question 32

describe the myotactic jaw reflexes.

Answer 32

- detected when stretched - afferent fibres send information through trigeminal nerve - to trigeminal mesencephalic nucleus - relay information - efferent fibres sent signal to contract the jaw

Question 33

describe the nociceptive jaw reflexes

Answer 33

protects the teeth from damaging biting forces - pain from teeth - afferent fibres to trigeminal nuclei - 2 responses: excite mylohyoid muscle to open jaw and inhibitory signals to masseter to stop contracting - relieve mouth of pain