Muscles Of Mastication - Regional Anatomy

Question 1

Principle muscles?

Answer 1

Four principle muscles:
- temporalis
- masseter
- lateral pterygoid
- medial pterygoid

Question 2

Accessory muscles?

Answer 2

• buccinator
• mylohyoid
• digastric

Question 3

Muscles of mastication

Answer 3

• Origin - O - non-moving attachment
• Insertion - I - moving attachment
• Shape - S
• Action of muscle contraction - A
• Nerve supply - N

Question 4

Temporalis

Answer 4

• O - whole of temporal fossa
• I - tip of coronoid process and whole anterior edge of ramus
• S - fan shaped muscle
• A - lifts mandible up and pulls it slightly backwards
• N - temporalis branch of mandibular division of trigeminal

Question 5

Masseter

Answer 5

• O - inferior border and whole inner surface of the zygomatic arch
• I - roughened area on outer aspect of ramus - in region of the angle of the mandible
• S - strong quadlerateral shaped muscle
• A - pulls mandible up and slightly forward - clenching
• N - masseter is branch of mandibular division of trigeminal

Question 6

Lateral pterygoid

Answer 6

• O - lateral surface of lateral pterygoid plate
• I - anterior surface of pterygoid fossa on neck of condole (n.b. Some fibres inserted into capsule and articular disc of TMJ)
• S - conical, short, thick
• A - together = pull condole forward, depressing or protruding mandible.
  Individually = swing mandible to opposite side
• N - lateral pterygoid branch of mandibular division of trigeminal

Question 7

Medial pterygoid

Answer 7

• O - medial surface surface of lateral pterygoid plate
• I roughened portion of inner aspect of ramus in region of angle of mandible
• S - broad, rectangular
• A - assist with elevating the mandible and clenching
• N - medial pterygoid branch of mandibular division of trigeminal

Question 8

Mylohyoid

Answer 8

• O - mylohyoid line
• I - posterior fibres = pass medially and downwards to body of hyoid bone
  anterior fibres = attach to fibres of opposite side, creating midline rather
• S - together give a flattened muscular floor to oral cavity
• A - depends on hyoid bone (n.b. swallowing)
• N - mylohyoid branch of mandibular division of trigeminal

Question 9

Digastric

Answer 9

• consists of 2 parts - anterior and posterior belly
  2 origins:
  O - mastoid notch (post)
  O - digastric fossa (ant)
• I - intermediate tendon of hyoid bone
• A - controls position of hyoid bone - can assist in depressing mandible against resisting force
• N - ant = mandibular division of trigeminal
  post = facial nerve

Question 10

Buccinator

Answer 10

• O - 5 parts:
  > maxillary alveolar ridge
  > pterygoid hamulus
  > pterygomandibular raphe
  > retromolar pad
  > external oblique line
• I - anteriorly into lateral aspect of orbicularis oris
• S - thick, flattened, horseshoe shaped muscle, bulk of cheek
• A - control food during mastication, facial expression
• N - buccaneers branch of facial

Question 11

Other muscles - stylohyoid

Answer 11

• O - styloid process
• I - greater horn of hyoid bone near junction with body
• A - fixation of hyoid - elevation and reaction of hyoid
• N - facial

Question 12

Other muscles

Answer 12

• O - inner surface of mandible in area of genial tubercles
• I - upper half of body of hyoid
• A - moves the hyoid bone
• N - hypoglossal