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Flashcards in oral function - muscles Deck (50)
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what are mandibular muscles

a different name for muscles of mastication
- masseter, temporalis, medial pterygoid and lateral pterygoid


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

because there are many other muscles involved in mastication


what is the origin of the masseter

zygomatic arch


what is the insertion of the masseter

lateral surface and angle of the mandible


what is the action of the masseter

elevates mandible


how do you examine the masseter

- 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


what is the origin of the temporalis

floor of the temporal fossa


what is the insertion of the temporalis

coronoid process and anterior border of ramus


what is the action of the temporalis

elevates and retracts the mandible


how can you examine the temporalis

- 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


what is the origin of the lateral pterygoid

from lateral surface of the lateral pterygoid plate


what is the insertion of the lateral pterygoid

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


what is the function of the lateral pterygoid

- 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)


where does the inferior belly of the lateral pterygoid attach

to the head of the condyle


where does the superior belly of the lateral pterygoid go

inserts into the intra-articular disc


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

because they have 'tired out' the lateral pterygoid muscle


what is most often the cause of a 'click'

spasm of the lateral pterygoid muscle


how can you examine the lateral pterygoid

- 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


what is the origin of the medial pterygoid

deep head - medial surface of the lateral pterygoid plate
superficial head - tuberosity of maxilla


what is the insertion of the medial pterygoid

medial surface of angle of the mandible


what is the action of the medial pterygoid

elevates and assists in protrusion of the mandible


why can't the medial pterygoid be palpated

because it sits on the inside of the jaw


does the medial pterygoid respond well to resistive movement tests



is there any reliable way of examining the medial pterygoid



what muscles are near the angle of the mandible

- masseter is on the lateral side
- medial pterygoid is on the mesial side


what can cause trismus

- 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


what should be hit when doing an ID block

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


what are the 2 movements of the TMJ

- rotation (initial opening)
- translation (wider opening)


what is rotation of the TMJ

- 1st movement
- hinge movement
- rotates around the hinge axis


what is translation of the TMJ

- 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