Anatomy and Function of Mastication Muscles

Oct 20, 2024

Lecture Notes: Muscles of Mastication

Introduction

  • Key muscles involved in mastication (chewing):
    • Temporalis
    • Masseter
    • Medial Pterygoid
    • Lateral Pterygoid
  • Discussion of origins, insertions, movements, innervations, and blood supply.

Anatomy of Mastication Muscles

Temporalis Muscle

  • Origin:
    • Temporal fossa (frontal, parietal, temporal, sphenoid bones)
  • Insertion:
    • Coronoid process of the mandible
  • Actions:
    • Elevates mandible (anterior and mid fibers)
    • Retracts mandible (posterior fibers)

Masseter Muscle

  • Origin:
    • Zygomatic arch (zygomatic and temporal bones)
  • Insertion:
    • Angle, ramus, and coronoid process of the mandible
  • Actions:
    • Elevates mandible
    • Slight protrusion of mandible

Medial Pterygoid Muscle

  • Origin:
    • Medial side of lateral pterygoid plate (sphenoid bone), palatine bone, maxilla
  • Insertion:
    • Inner part of the angle and ramus of the mandible
  • Actions:
    • Elevates mandible
    • Protrudes mandible
    • Moves mandible side-to-side (unilateral contraction)

Lateral Pterygoid Muscle

  • Origin:
    • Lateral side of lateral pterygoid plate (sphenoid bone), maxilla, palatine bone
  • Insertion:
    • Condylar process of the mandible, TMJ joint capsule and articular disc
  • Actions:
    • Protrudes mandible
    • Depresses mandible
    • Side-to-side movements (unilateral contraction)

Innervation

  • All muscles innervated by the mandibular branch of the trigeminal nerve (Cranial Nerve V)

Blood Supply

  • Temporalis: Maxillary artery and superficial temporal artery
  • Masseter: Masseteric artery (branch of maxillary artery)
  • Pterygoids: Branches from facial and maxillary arteries

Accessory Muscles of Mastication

  • Buccinator Muscle: Assists in pushing food back into the mouth
  • Suprahyoid Muscles (mylohyoid, geniohyoid, digastric): Assist in depressing the mandible
  • Infrahyoid Muscles (sternohyoid, sternothyroid, omohyoid): Stabilize the hyoid bone

Conclusion

  • Recap of all the key muscles, their origins, insertions, actions, innervations, and blood supply.
  • Resources recommended: Anatomy.app for further learning.

These notes summarize the anatomy and function of the muscles of mastication, critical for understanding the mechanics of chewing and jaw movement.