TMJ

Question 1

jaw function

Answer 1

• for speech
• mastication
• involves moving mandible around
• jaw can be elevated, dpressed, protruded, and moved from side to side
• range of motion supported by TMJ and muscles of mastication

Question 2

jaw opening muscles

Answer 2

• open mouth
• important for shaping oral cavity
• breathing inserting food and vocalizing

Question 3

jaw closing muscles

Answer 3

• crushing food
• assisting in production of certain sounds
• jaw closers also participate in rotational grinding of food and moving jaw laterally

Question 4

TMJ properties

Answer 4

• unique and complex
• only joint that must work simultaneously as a bilateral pair
• has articular disc that divides into two compartments
• only other joint with disc is sternocalvicular
• only movable joint of skull
• move mandivle at articulation point between condyle and temporal fossa

Question 5

classified as a _____ joint

Answer 5

• ginglymoarthroidal
• ginglymo - hinge joint allowing rotational motion
• arthroidal - plane allowing sliding
• can also rotate joint
• lower joint between condyle and disc involved in rotational movements
• upper compartments between disc and temporal fossa involved in translational movements
• both filled with synovial fluid

Question 6

joint allows

Answer 6

• mouth opening
• rotational motion simplified and measured as inferior-superior distance
• jaw lowering
• lower compartment of joint
• jaw to closure 20 mm
• after 20 mm upper compartment engaged
• then articular disc and condyle slide forward to allow greater mouth opening

Question 7

when jaw rotates

Answer 7

• muscles contract on both sides
• bilateral contraction allows opening and closing
• gravity assists in opening
• elastic recoil assists in closing
• symmetrical contraction more common for speech and opening mouth for food
• lateral motion accomplished by asymmetrical activity
• lateral pterygoid pulls condyle laterally while opposite side relaxes

Question 8

TMJ capsule

Answer 8

• fibrous membrane surrounding joint

- encapsulates temporal portion, articular disc, condyle head & condyle neck

Question 9

articular disc

Answer 9

• derived from capsule
• splits joint in 2 compartments
• bioconcave shape
• jaw pain from pressure on disc
• condyle pushes disc against temporal bone

Question 10

TMJ ligaments

Answer 10

• largest = temporomandibular ligament
• accessory:
• stylomandibular
• sphenomandibular - runs from spine of sphenoid to lingula of mandible
• *define normal range of mandibular motion
• beyond range painful

Question 11

innervation

Answer 11

-sensory V3 of trigrminal 
auricular and masseteric branches 
-peopriception - position of jaw
muscle spindles 
-joint tension
golgi tendon organs
-pain
free nerve ending surrounding joint
**nerve fibers surround capsule but dont enter joint as it would disrupt function
-motor innervation 
-V3 trigeminal 
-all muscles that move jaw

Question 12

TMJ syndrome

Answer 12

• umbrella term for acute or chronic inflammation of joint
• pain syndrome
• disc displacement between condyle and fossa
• carries condyle forward “pops”
• pain and movement limitation

Question 13

syndrome linked to

Answer 13

• external factors place strain on jaw
• trauma
• bruxation - teeth grinding
• excessive gum chewing/nail biting
• degenerative joint diseases
• lack of overbite

Question 14

jaw opening muscles

Answer 14

• anterior belly of digastric
• lateral pterygoid
• geniohyoid
• mylohyoid
• platysma

Question 15

jaw closers

Answer 15

• masseter
• temporalis
• medial pterygoid

Question 16

lateral motions

Answer 16

• synergistic muscle actions
• temporalis
• medial pterygoid
• lateral pterygoid

Question 17

masseter

Answer 17

• thick quadrilateral muscle
• easily palpated
• superficial portion from zygomatic process of maxilla to angle and lower half of ramus
• deep portion is smaller
• course: zygomatic arch to upper half of ramus and lateral coronoid process
• innervated mandibular division CN V
• largest and strongest muscle
• elevates, retracts and closes jaw
• most rapid reflex in body
• minimal role in speech

Question 18

temporalis

Answer 18

• arises from temporal fossa
• passes within zygomatic arch
• inserts on coronoid process
• innervated mandibular branch CN V
• contraction of temporalis elevates mandible
• strong

Question 19

lateral pterygoid

Answer 19

• two bellies
• originates lateral surface of lateral pterygoid plate and partially from sphenoid bone
• inferior head inserts pterygoid fovea on neck of condyle
• superior head inserts on articular disc and fibrous capsule of TMJ
• only muscle attaching to ramus or angle that helps open jaw
• assist in moving jaw form side to side

Question 20

medial pterygoid

Answer 20

• originates medial surface of lateral pterygoid plate
• inserts on lower and posterior ramus and angle
• on medial surface
• course of masseter
• with masseter forms sling around ramus and angle
• medial/internal masseter
• assists in jaw closure force
• assists lateral pterygoid in side movement
• innervated mandibular branch CN V

Question 21

anterior belly of digastric

Answer 21

• course aponeurotic leep of tissue on body and greater cornu of hyoid
• inserts on mental spine of mandible
• innervated mandibular branch CN V
• assists in jaw opening when hyoid is in place

Question 22

geniohyoid

Answer 22

• arise inferior mental spine
• courses backwards and downwards to insert on body of hyoid
• suprahyoid
• assist in opening jaw when hyoid is fixed
• inervated by CN XII
• contributes to medial portion of floor of mouth

Question 23

mylohyoid

Answer 23

• flat triangular muscle
• arises mylohyoid line on masseter body
• suprahyoid
• form floor of the mouth
• median fibrous raphe
• assist in opening jaw when hyoid fixed
• innervated madibular division of V3 - CN V

Question 24

platysma

Answer 24

• thin flat sheet of muscle
• most superficial muscle
• covers large portion of anterior neck and surrounding area
• fibers attach to anterior mandible, skin, subcutaneous tissue
• innervated cervical branch CN VII
• actions:
• wrinkle neck
• assist in jaw opening
• pulls down lower lip and corners of mouth

Question 25

jaw functions in speech

Answer 25

• stable platform for tongue and lip motions
• jaw stabilizes first
• makes more refined speech movements possible
• wider opening of mouth assists in acoustic radiation
• combined action of lateral pterygoid +ABD +gravity
• weak closing forces mediated by temporalis
• lateral motions of jaw highly functional in speech
• propropception from jaw closers critical role in learning jaw position and transmitting jaw position info

Question 26

TMJ disorder treatment

Answer 26

-varied because not completely understood
-pharmacologic
-eliminate bad oral habits
-jaw stretching therapy
-mandibular repositioning
splint or surgical correction of bite

Question 27

jaw muscles of speech

Answer 27

• still difficult to ID which jaw muscles are more involved in speech
• more likely to be jaw openers
• could be combined action of ABD+gravity
• weak closing forces may be mediated by temporalis
• some lateral motions of jaw in highly functional speech
• proprioception from jaw closers may have a critical role in learning jaw position and transmitting jaw position info