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movement systemskillscheck > TMJ > Flashcards

TMJ Flashcards

1
Q

Which bones contribute to the formation of the TMJ?

A

Sphenoid, Zygomatic, Maxilla, Mandible, Temporal

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2
Q

actions of masseter

A

Unilateral – elevation and ipsilateral deviation
Bilateral – elevation and forceful closure

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3
Q

action of temporalis

A

Unilateral – elevation, retraction, ipsilateral deviation
Bilateral – elevation and retraction

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4
Q

action of medial pterygoid

A

Unilateral – elevation and contralateral deviation (pulls the ramus medially causing contralateral deviation)
Bilateral – elevation
Also capable of slight protrusion d/t fibers oriented in the sagittal plane
Synergist with Lateral pterygoid

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5
Q

action of lateral pterygoid

A

Unilateral – protrusion and contralateral deviation
Bilateral – protrusion
Superior head attaches directly to the intraarticular disc and produces anterior translation of the disc that occur in the early stages of mandibular depression

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6
Q

what muscles control anterior and posterior translation of the mandible

A

Lateral pterygoid and posterior fibers of the temporalis

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7
Q

hyperactivity of the superior head of the lateral pterygoid produces

A

excessive translation of the disc

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8
Q

hyperactivity of the inferior head of the lateral pterygoid produces

A

excessive translation of the mandible with respect to the disc

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9
Q

is the medial pterygoid a synergist with the lateral pterygoid

A

yes

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10
Q

how is stability of the TMJ provided

A

Stability through ligaments – lateral ligament comprised of deep horizontal fibers (limit posterior translation) and superficial oblique fibers (prevent inferior translation)

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11
Q

what part of TMJ provides cushion

A

articular disc

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12
Q

how many degrees of freedom does the TMJ have

A

3

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13
Q

what are the motions of the TMJ

A

Protrusion/retrusion – mandible moves anteriorly and posteriorly respectively
Opening/closing – mandibular depression and elevation respectively
Lateral deviation – side to side motion

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14
Q

describe arthrokinematics that occur at TMJ with depression/opening early phase

A

mandibular condyle rolls posteriorly on the articular disc, rotation

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15
Q

describe arthrokinematics that occur at TMJ with depression/opening late phase

A

anterior slide and translation of the mandibular condyle and disc (as one) translating on the articular eminence

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16
Q

describe arthrokinematics that occur at TMJ with protrusion

A

Mandible and disc slide together along the downward slope of the articular eminence

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17
Q

describe arthrokinematics that occur at TMJ with lateral excursion

A

Rotation about a vertical axis
Ipsilateral excursion, pivot point about a vertical axis
Contralateral side rotates anteriorly and medially

18
Q

muscles of right lateral excursion

A

Left medial and lateral pterygoid, right masseter and temporalis

19
Q

muscles of left lateral excursion

A

Right medial and lateral pterygoid, left masseter and temporalis

20
Q

muscles of opening (depression)

A

Lateral pterygoid for protrusion, suprahyoid and infrahyoid. Gravity is the prime mover

21
Q

muscles of closing (elevation)

A

Bilateral masseter, temporalis and medial pterygoid

22
Q

muscles of protrusion

A

lateral pterygoid

23
Q

muscles of retrustion

A

temporalis - posterior fibers

24
Q

why are the infrahydoid muscles active when opening the mouth

A

Suprahyoid muscles function as mandibular depressors (mouth opening) when the hyoid bone is fixed by the infrahyoid muscles

25
Q

why eccentric activation is needed from the lateral pterygoid when closing the mouth.

A

Important for slowing down mouth closing. Don’t want rapid closing of the mouth because that might pinch the posterior tissues – retrodiscal laminae and fat pad (highly sensitive)

26
Q

What important function does the lateral pterygoid perform?

A

Eccentric control during mouth closing – slows down retrusion, allows for precise synchronization between the movement of the mandible and disc

27
Q

what are the attachments for the articular disc

A

Anterior attachment: lateral pterygoid muscle
(superior head)
Posterior attachment: through retro-discal laminae

28
Q

what does the articular disc do

A
  • provide cushion and increase congruency
  • Separates the joint into two synovial cavities:
  • Inferior jt cavity: between the mandibular
    condyle and the disc
  • Superior jt cavity: between the disc and the
    articular eminence and manibular fossa
29
Q

what is the purpose of accessory ligaments

A

– sphenomandibular and
stylomandibular ligaments
- Attach to the medial side of the joint capsule
- Help to suspend the mandible from the
cranium.
- They have limited role in TMJ function.

30
Q

what is lateral excursion

A

side to side translation of the condyle and disc within the fossa

avg 11mm of max. unilateral excursion
usually combined w other translations and rotations

31
Q

arthrokinematics during rotation

A

the mandibular condyle rolls relative to the articular disc

32
Q

arthrokinematics during translation

A

the mandibular condyle and the disc slide together on the articular eminence of the maxilla

33
Q

what initiates the late phase of mandibular depression/opening

A

increased tension on the lateral ligament (final 50-65% of ROM)

34
Q

what happens during left lateral excursion

A

the left condyle forms pivot point of rotation (about a vertical axis) and
right condyle rotates anteriorly and medially

35
Q

internal forces of TMJ in the static position

A

the mastication muscles must be active to balance the gravity

36
Q

prime mover of opening the mouth

A

gravity - downward rotation torque
lateral pterygoid - protrusion

37
Q

stabilizers of opening the mouth

A

infrahyoid stabilizes the hyoid bone

38
Q

prime movers in closing the mouth

A

masseter, medial pterygoid, temporalis

39
Q

antagonist in closing the mouth

A

Lateral pterygoid
superior head:
eccentric, slows down
retrusion

40
Q

when is the bite force the greatest

A

when the bite occurs close to the molars

41
Q

when the bite force is the least it occurs at __ and why

A

it is occurs at the incisors
- Decreased bite force with incisor bite appears due to
decrease in ms mechanical advantage and probably
inhibition of the temporalis ms (incisor bite requires jaw
protrusion)

movement systemskillscheck (5 decks)

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