Oral Functions 1 - muscles Flashcards
List the mandibular muscles.
Masseter
Temporalis
Medial pterygid
Lateral pterygoid
What is the origin and insertion of the masseter?
Origin - Zygomatic arch
Insertion: Angle and lateral surface of the mandible.
What is the action of the masseter?
Elevates the mandible
How do you examine the masseter?
1 finger intra-orally and another finger on the cheek, extra-orally.
What is the origin and insertion of the Temporalis?
Origin - Floor of the temporal fossa
Insertion - Coronoid process and the anterior border of the ramus
What is the action of the temporalis?
Elevation and retraction of the mandible
How do you examine the temporalis?
Ask patient to clench.
Palpate above the ear and in the supra-orbital region.
What is the origin and insertion of the lateral pterygoid?
Origin - Lateral surface of the lateral pterygoid plate
Insertion via 2 independent heads:
Superior belly - Intra-articular disc
Inferior belly - anterior border of the condyle
What is the function of the lateral pterygoid?
Opening/depressing the mandible
How do you examine the lateral pterygoid?
Resisted movement
What is the origin and insertion of the medial pterygoid?
Origin:
Deep - medial surface of lateral pterygoid plate
Superficial - Tuberosity of the maxilla
Insertion - angle of the mandible
What is the function of the medial pterygoid?
Elevation and protrusion of the mandible
How do you examine the medial pterygoid?
Cant examine
A spasm in which muscle is responsible for a jaw click?
Lateral pterygoid
What muscle is commonly anaesthetised accidentally in an Inferior alveolar nerve block?
Medial pterygoid
How many movements is there in the opening of the TMJ? Explain them.
2 Movements:
Rotation - initial (hinge) opening
Translation - wider opening
Protrusion: condyles moves out of the fossae and along the articular eminences.
or
Retrusion: Condyle moves from the articular eminence back to the fossae.
What chart shows the border movements of the mandible?
Envelope chart
What factors affect the maximum biting force?
Psychological factors - fear of tooth fracture
Muscle mass - larger muscles = greater forces
List the muscle fibre types present in the jaw and what forces they are responsible for.
Type 1 - slower forces
Type 2 - stronger and faster forces
What fibres are predominantly present in people with square jaws?
Type 2 fibres - stronger and faster forces
In terms of tooth type and position; which supply larger forces?
Teeth that are closer to the muscles generating the forces and the TMJ.
I.e. 1st permanent molar has the greatest biting force.
Teeth that have the greatest root area and PDL support
What teeth have poor biting forces and why?
Anteriors i.e. centrals and laterals
Further away from the TMJ and the muscles generating the forces.
Less root surface area
List the suprahyoid muscles.
Geniohyoid
Stylohyoid
Mylohyoid
Digastric
List the infrahyoid muscles
Sternohyoid
Sternothyroid
Omohyoid
thyrohyoid
