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BDS2 - BAMS > oral function - muscles > Flashcards

oral function - muscles Flashcards

1
Q

what are mandibular muscles

A

a different name for muscles of mastication

- masseter, temporalis, medial pterygoid and lateral pterygoid

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2
Q

what is misleading about the 4 muscles masseter, temporals, medial pterygoid and lateral pterygoid being named muscles of mastication?

A

because there are many other muscles involved in mastication

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3
Q

what is the origin of the masseter

A

zygomatic arch

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4
Q

what is the insertion of the masseter

A

lateral surface and angle of the mandible

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5
Q

what is the action of the masseter

A

elevates mandible

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6
Q

how do you examine the masseter

A
  • it is tender in patients with a clenching habit

- place one finer intra-orally and the other on the cheek (zygomatic arch) and get patients to clench

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7
Q

what is the origin of the temporalis

A

floor of the temporal fossa

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8
Q

what is the insertion of the temporalis

A

coronoid process and anterior border of ramus

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9
Q

what is the action of the temporalis

A

elevates and retracts the mandible

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10
Q

how can you examine the temporalis

A
  • it can be tender in patients with a bruxism habit
  • examine the origin not insertion
  • palpate the origin by asking the patient to clench their teeth together
  • digital palpation is performed between the superior and inferior temporal lines just above the ear, extension forwards towards the supra-orbital region
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11
Q

what is the origin of the lateral pterygoid

A

from lateral surface of the lateral pterygoid plate

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12
Q

what is the insertion of the lateral pterygoid

A

anterior border of the condyle and intra-articular disc via two independent heads (superior and inferior heads)

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13
Q

what is the function of the lateral pterygoid

A
  • protrudes and laterally deviates the mandible and the inferior head functions with the mandibular depressions during openings
  • lateral movement and opening of the jaw (depression of the jaw)
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14
Q

where does the inferior belly of the lateral pterygoid attach

A

to the head of the condyle

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15
Q

where does the superior belly of the lateral pterygoid go

A

inserts into the intra-articular disc

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16
Q

why do those who grind their teeth overnight sometimes wake up unable to open their mouth fully

A

because they have ‘tired out’ the lateral pterygoid muscle

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17
Q

what is most often the cause of a ‘click’

A

spasm of the lateral pterygoid muscle

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18
Q

how can you examine the lateral pterygoid

A
  • it is not accessible to palpitation as its inside
  • nest examined by recording its response to resisted movement
  • there is good correlation between resisted movement test and muscle being tender to palpation
  • if it hurts or can’t resist movement, then muscle is not right
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19
Q

what is the origin of the medial pterygoid

A

deep head - medial surface of the lateral pterygoid plate

superficial head - tuberosity of maxilla

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20
Q

what is the insertion of the medial pterygoid

A

medial surface of angle of the mandible

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21
Q

what is the action of the medial pterygoid

A

elevates and assists in protrusion of the mandible

22
Q

why can’t the medial pterygoid be palpated

A

because it sits on the inside of the jaw

23
Q

does the medial pterygoid respond well to resistive movement tests

A

no

24
Q

is there any reliable way of examining the medial pterygoid

A

no

25
Q

what muscles are near the angle of the mandible

A
  • masseter is on the lateral side

- medial pterygoid is on the mesial side

26
Q

what can cause trismus

A
  • if the medial pterygoid muscle is accidentally hit when doing an injection
  • occurs when carrying out inferior alveolar nerve block (ID block)
  • causes inability to open mouth to the same extent as before
27
Q

what should be hit when doing an ID block

A

bone, ensures correct position within the pterygomandibular triangle and not hit the soft tissues

28
Q

what are the 2 movements of the TMJ

A
  • rotation (initial opening)

- translation (wider opening)

29
Q

what is rotation of the TMJ

A
  • 1st movement
  • hinge movement
  • rotates around the hinge axis
30
Q

what is translation of the TMJ

A
  • 2nd movement
  • protrusive or retrusive movements
  • as mandible moves during protrusion, both condyles leave their fosse and move forward along the articular eminences
  • when mandible retrudes, both condyles leave eminences and move back into their respective fosse
31
Q

what is the outline of the movement of the TMJ called

A

the fossae envelope

32
Q

who founded the fossae envelope

A

Ulf Posselt in 1953

- he got graphical recordings in the occlusal and sagittal plane for the movement and all had the same shape of envelope

33
Q

what is the maximum biting/clenching forces

A
  • varies between teeth
  • maximum between 200-700N in molars
    (forces of 1200-1500N reported in Eskimo’s and world record is 4300N)
34
Q

how can psychological factors affect biting/clenching forces

A
  • fear of tooth fracture when max forces are used

- limits max forces used

35
Q

what other factors can affect maximum biting/clenching forces

A
  • muscle mass = bigger muscles cause larger forces
  • parafunction = bruxism, can fracture tooth with high occlusal forces and can get hypertrophic masseter muscle from excessive use
36
Q

what are the muscle fibre types

A
  • type 1 = slow, low forces
  • type 2 = fast, stronger forces
  • sub types = IIA, IIX, IIB
37
Q

what is the most predominant fibre type

A
  • predominant fibre type varies depending on jaw morphology, diet etc
  • there is evidence however that people with squarer jaws have more type II fibres and can generate stronger bite
38
Q

where is greatest biting forces generated

A

between 1st molars

39
Q

why do 1st molars have greatest biting force

A
  • they are closer to the muscle generating the force and the fulcrum so
  • this means that only a small amount of force is needed here to break food, if you bit food at the front of the mouth, a much larger force would be needed which could then fracture the tooth
40
Q

what support does the root area of a tooth have

A

PDL support

41
Q

what are some other muscles in mastication

A
  • supra hyoid
  • infra hyoid
  • hyoid bone
  • tongue muscles
  • facial muscles
42
Q

what are the supra hyoid muscles

A
  • digastric
  • mylohyoid
  • geniohyoid
  • stylohyoid
43
Q

what are the infra hyoid muscles

A
  • ‘strap muscles’
  • sternohyoid
  • omohyoid
  • thyrohyoid
  • sternothyroid
44
Q

what happens with the hyoid bone

A
  • when the hyoid bone is fixed by contraction of the infra hyoids, the supra hyoids (apart from the stylohyoid) act as depressors
45
Q

what are the 2 types of tongue muscles

A
  • intrinsic and extrinsic
46
Q

what are the intrinsic tongue muscles and what do they do

A
  • longitudinal, vertical and transverse

- alter shape

47
Q

what are the extrinsic tongue muscles and what do they do

A
  • genioglossus, hypoglossus, palatoglossus, styloglossus

- alter shape and position

48
Q

what is the main role of facial muscles

A

for expression

49
Q

what is an additional role of some of the facial muscles

A

keeps the blogs in the oral cavity

50
Q

which facial muscles keep the bolus in the oral cavity

A
  • orbicularis oris

- buccinator

BDS2 - BAMS (18 decks)

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