Mandibular Muscles Flashcards
What are muscles of mastication known as and why?
Mandibular muscles- more muscles involved in mastications
Why do we need to check for abnormalities in TMJ before doing fillings?
Can lead to fracture of fillings
What is the most powerful muscle in the body?
Masseter
How much forces can the masseter carry?
Up to 50N
What is the origin, insertion and action of the masseter?
Origin: zygomatic arch
Insertion: Lateral surface and angle of mandible
Action: Elevates mandible
How is the masseter examined?
Palpate one finger intra-orally and one on the cheek. 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 is the temporalis examined?
Tender in patients with bruxist habits. Palpate between between superior and inferior temporal lines above ear extending forward towards the supra-orbital region and ask patient to clench.
What is the origin, insertion and action of lateral pterygoid?
Origin: lateral surface of lateral pterygoid plate
Insertion: anterior border of condyle and infra-articular disc via 2 heads
Action: protrudes and laterally deviates the mandible and the inferior head functions with the mandibular depressors during openings.
Where does the inferior and superior bellies of the lateral pterygoid insert?
Inferior: head of the condyle
Superior: intra- articular disc
What causes a clicking sound?
Spasm in superior belly of lateral pterygoid pulling on the disc.
How is the lateral pterygoid examined?
Record its response to resisted movement.
What is the origin, insertion and action of the medial pterygoid?
Origin: the deep head- medial surface of LP plate, the superficial head-tuberosity of maxilla
Insertion: medial surface of angle of mandible
Action: elevates and assists in protrusion of mandible
How is the medial pterygoid examined?
It cannot be examined.
What are the movements of the TMJ and what are they collectively called?
Possult’s envelope- rotation and translation
What is Possult’s envelope and what does it represent?
Border movements of the jaw, represent pressure protrusion of the mandible
Which tooth has the greatest bite force and why?
First molar- proximity to the hinge
What is the maximum biting force between molars?
200-700N
What are the suprahyoid muscles and which of them act as jaw depressors when the infrahyoid muscles contract
Jaw depressors- digastric, mylohyoid, geniohyoid
Stylohyoid
How are the suprahyoid and infrahyoid muscles involved in mastication?
Stabilise bone during mastication
What are the infrahyoid muscles?
Sternohyoid, omohyoid, thyrohyoid, sternohyoid
What does the intrinsic tongue muscle do what are the different types?
Alter shape- longitudinal, vertical, transverse
What does the extrinsic tongue muscle do and what are the different types?
Alter shape and position of tongue- genioglossus, hypoglossus, palatoglossus, styloglossus
What are the facial muscles for?
Mainly for expression, important in chewing
