Muscles of Mastication

Question 1

what are the muscles of mastication

Answer 1

1. masseter
2. temporalis
3. lateral pterygoid
4. medial pterygoid
5. suprahyoid and infrahyoid muscles

Question 2

Masseter - origin, insertion and function

Answer 2

• origin = zygomatic arch
• insertion = lateral surface of the angle of the mandible
• function = elevate the mandible

Question 3

temporalis - origin, insertion and function

Answer 3

• origin = floor of temporal fossa
• insertion = coronoid process and anterior body of the ramus
• function = elevates and retracts mandible

Question 4

lateral pterygoid - origin, insertion and function

Answer 4

• origin = lateral surface of lateral pterygoid plate
• insertion
  i. superior belly inserts into intra-articular disk of condyle
  ii. inferior belly to the head of the condyle
  function = protrusion, lateral movement and inferior belly helps with mandible depressions

Question 5

medial pterygoid - origin, insertion and function

Answer 5

• origin =
  i. deep head = medial surface of lateral pterygoid plate
  ii. superficial head = tuberosity of maxilla
• insertion = medial surface of the angle of the mandible
• function = elevates and assists in protrusion of mandible

Question 6

describe TMJ movements

Answer 6

1. rotational = hinge movement for opening jaw slightly
2. translation = protrusive/retrusive movements for opening mouth wider, condyles leave their fossa and move along articular eminences and leave eminences when retrude
   - diagram showing movement = Posselt’s envelope

Question 7

types of muscle fibre effecting mastication force

Answer 7

• type I = slow low forces
• type II = ast stronger forces
• sub types = IIA, IIX, IIB

Question 8

name and describethe function of the suprahyoid and infrahyroid muscles

Answer 8

suprahyoid muscles
      - for jaw depression = digastric, mylohoid and geniohoid
      - stylohoid
infrahyoid (strap muscles)
- sternohyoid
- omohyoid 
- thyrohyoid 
- sternothyoid

Question 9

name muscles of the tongue and what the groups do

Answer 9

• intrinsic (alter shape) = longitudinal, vertical and transverse
• extrinsic (alter shape and position) = genioglossus, hyoglossus, palatoglossus, styloglossus

Question 10

name two facial muscles that help control a food bolus and prevent spillage

Answer 10

• orbicularis oris

- buccinator