16 - TMJ and muscles of mastication Flashcards

1
Q

What is the function of the mandible?

A
  • site for muscle attachments
  • foramina for passage of neuromuscular structures
  • teeth in alveolar processes
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2
Q

What is the mandibular symphysis?

A

Fused bone, as the mandible is in two parts when born

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3
Q

Describe the location of the TMJ.

A
  • articulates in the mandibular fossa of temporal bone
  • condylar process of the mandible
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4
Q

Describe the TMJ.

A
  • modified hinge (atypical) synovial joint
  • articular surfaces covered in fibrocartilage (not hyaline)
  • fibrocartilaginous articular disc separates joint into superior and inferior articular cavities
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5
Q

Describe the ligaments associated with the TMJ.

A
  • 2 extrinsic and 1 intrinsic
  • connect mandible to cranium
  • sphenomandibular ligament
  • stylomandibuiar ligament
  • lateral ligament
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6
Q

What is the role of the sphenomandibular ligament?

A
  • primary passive support of mandible
  • helps swing mandible
  • attaches from the spine of the sphenoid bone to the lingula
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7
Q

What is the role of the stylomandibular ligament?

A
  • thickening of the parotid capsule
  • doesn’t contribute to strength
  • attaches from the styloid process to the angle of the mandible
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8
Q

What is the role of the lateral ligament?

A
  • strengthen TMJ laterally
  • works with the postglenoid tubercle to prevent posterior dislocation
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9
Q

What are the 5 movements of the mandible?

A
  • protrusion
  • retraction
  • elevation
  • depression
  • lateral
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10
Q

What muscles aid protrusion of the mandible?

A

Lateral pterygoid (assisted by medial pterygoid)

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11
Q

What muscles aid retraction of the mandible?

A
  • posterior fibres of temporalis
  • deep part of masseter
  • geniohyoid
  • digastric
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12
Q

What muscles aid elevation of the mandible?

A
  • temporalis
  • masseter
  • medial pterygoid
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13
Q

What muscles aid depression of the mandible?

A
  • digastric
  • geniohyoid
  • mylohyoid
  • (infrahyoid muscles work to fix the hyoid so that the mandible opens against resistance)
  • (gravity)
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14
Q

What muscles aid the lateral movements of the mandible?

A
  • ipsilateral temporalis
  • contralateral medial and lateral pterygoid
  • masseter
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15
Q

Which cavity of the TMJ is active during protrusion?

A
  • superior cavity
  • gliding movement between temporal bone and articular disc
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16
Q

Which cavity of the TMJ is active during retraction?

A
  • superior cavity
  • gliding movement between temporal bone and articular disc
17
Q

Which cavity of the TMJ is active during elevation?

A
  • inferior cavity
  • hinge and rotational movement between head of mandible and articular disc
18
Q

Which cavity of the TMJ is active during depression?

A
  • inferior cavity
  • hinge and rotational movement between head of mandible and articular disc
19
Q

What type of dislocation is most common in the TMJ?

A

Anterior dislocation

20
Q

What causes dislocation of the TMJ?

A
  • excessive contraction of lateral pterygoid
  • adequate posterior support
  • poor anterior support and no stop for head of condyle
21
Q

What nerve supplies the muscles of mastication?

A

CN V3

22
Q

What is the origin of temporalis?

A

Temporal fossa and fascia

23
Q

What is the origin of masseter?

A

Maxillary process of zygomatic bone and anterior 2/3 of inferior border of zygomatic arch

24
Q

What is the origin of medial pterygoid?

A

Deep head - medial surface of lateral pterygoid late (sphenoid bone)
Superficial head - pyramidal process of palatine bone

25
Q

What is the origin of lateral pterygoid?

A

Upper head - infratemporal surface of great wing of sphenoid bone
Lower head - lateral surface of lateral pterygoid plate (sphenoid bone)

26
Q

What is the insertion of temporalis?

A

Coronoid process of mandible and anterior border of ramus

27
Q

What is the insertion of masseter?

A

Angle and lateral surface of ramus

28
Q

What is the insertion of medial pterygoid?

A

Medial surface of mandible and angle

29
Q

What is the insertion of lateral pterygoid?

A

Upper head - capsule of TMJ and articular disc
Lower head - pterygoid fovea

30
Q

What is the action of temporalis?

A

Retracts and elevates mandible

31
Q

What is the action of masseter?

A

Elevate mandible

32
Q

What is the action of medial pterygoid?

A

Elevate and assist with lateral movement of mandible

33
Q

What is the action of lateral pterygoid?

A

Protrude, depress and assist with lateral movement of mandible