Oral Functions: Muscles Flashcards
What are the mandibular muscles?
lateral pterygoid
medial pterygoid
masseter
temporalis
What is the origin, insertion and action of the masseter?
Origin - zygomatic arch
Insertion - ramus
and angle of mandible
Action - elevates mandible
How to examine the masseter muscle?
place one finger intra-orally and the other on the cheek
check the bulk of the muscle, it is tender in patients who have a clenching habit
What is the origin, insertion and action of the temporalis?
Origin - floor of temporal fossa
Insertion - coronoid process and
anterior border of ramus
Action - elevates and retracts mandible
How to examine the temporalis?
Palpate its origin by asking the patient to clench the teeth together.
Digital palpation is performed between the superior and inferior temporal lines just above the ear, extending forwards towards the supra-orbital region.
It is tender in patients who have a bruxist habit
What is the origin, insertion and action of the lateral pterygoid?
Origin: surface of the greater wing of the sphenoid and lateral surface of the lateral pterygoid plate
Insertion: anterior border of the condyle and intra-articular disc
via two independent heads
Action: protrudes and laterally deviates the mandible. depresses the mandible
Where do the inferior/ superior belly of the lateral pterygoid attach?
- The inferior belly of the lateral pterygoid attaches to the head of the condyle.
- The superior belly inserts into the intra- articular disc
How can you examine the lateral pterygoid?
Not accessible to manual palpation
Best examined by recording its response to resisted movement.
There is a good correlation between the resisted movement test and the muscle being tender to palpation.
What is the origin, insertion and action of the medial pterygoid?
Origin - deep head: medial surface of lateral pterygoid plate ; superficial head: tuberosity of maxilla
Insertion - medial surface of angle of mandible
Action - elevates and assists in protrusion of the
mandible
How to examine the medial pterygoid?
Because of the location of the medial pterygoid, on the inside of the jaw, this muscle is not available for palpation.
It also does not respond well to resistive movement tests.
Therefore, unfortunately, there is no reliable way of examining this muscle.
When injecting a nerve block, what may happen and what can prevent this?
Accidentally hit the medial pterygoid with the needle causes trismus (spasm of the jaw muscles, causing the mouth to remain tightly closed)
therefore
Bone should be contacted to ensure correct position within the pterygomandibular triangle and not t hit soft tissues.
What are the two movements of TMJ?
- Rotation - initial opening
- Translation-wider opening
What type of movement is rotation?
hinge movement
What type of movements is translation?
Sliding
Wider opening: Protrusive or retrusive movements
How does translation happen?
As the mandible moves during protrusion, both condyles leave their fossae and move forward along the articular eminences.
When the mandible retrudes, both condyles leave the eminences and move back into their respective fossae
What is Posselt’s Envelope of Motion?
refers to the full TMJ movement which involves rotation + translation.
(max movement jaw can create)
Which teeth have max biting force?
molars (200-700n)
What psychological factors could limit max biting force recorded?
Fear of tooth fracture when maximum forces are used
What oral disorder could too much force cause?
parafunction (bruxism)
What are the types of muscle fibres and what are their qualities?
- Type 1 = Slow, low forces.
- Type 2 = Fast, stronger forces.
- Sub-types (IIA, IIB, IIX) = Predominant fibre type varies, often dependent on jaw morphology and diet
What fibres do people with squarer jaws have more of?
type 2
Where is the greated bit force generated and why?
- Greatest bite forces generated between 1st molars
- Position relative to TMJ and muscles (Molars are nearer the force generating muscles and the fulcrum (TMJ)
- Root area (PDL support)
What are the suprahyoid muscles?
– Digastric
– Mylohyoid
– Geniohyoid
– Stylohyoid
What groups of muscles surround the hyoid bone?
infrahyoid (strap) muscles
suprahyoid
What are the infrahyoid (strap) muscles?
–Sternohyoid
–Omohyoid
–Thyrohyoid
–Sternothyroid
What muscles depress the jaw?
diagastric
mylohyoid
geniohyoid
lateral pterygoid
What are the two types of tongue muscles and what do they do?
intrinsic (alter shape of tongue)
extrinsic (alter shape, position)
What are the intrinsic muscles?
Longitudinal, vertical, transverse
What are the extrinsic muscles?
Genioglossus
Hyoglossus
Palatoglossus
Styloglossus
What facial muscles help control food bolus and spillage?
–Orbicularis oris
– Buccinator
