Muscles: Location, Origin, Insertion and Action

Masseter

• Location: Side of the cheek
• Origin: Zygomatic arch (cheek bone)
• Insertion: Angle and ramus of mandible
• Action: Elevates the mandible, closing the jaw

Temporalis

• Location: Side of the skull (temporal lobe area)
• Action: Elevates and retracts the mandible

Trapezius

• Location: Upper back and neck
• Action:
  • Elevates the scapula
  • Assists in upward rotation of scapula
  • Retracts scapula
  • Depress scapula
  • Assists in upward rotation

Sternocleidomastoid

• Location: Side of the neck
• Origin: Manubrium of the sternum, medial portion of clavicle
• Insertion: Mastoid process of the temporal bone
• Action:
  • Unilateral contraction which rotates the head to opposite sides
  • Tilts

Frontalis

• Location: Forehead (occipitofrontalis muscle)
• Action:
  • Raises the eyebrows
  • Wrinkles forehead skin

Orbicularis Oculi

• Location: Muscle surrounding the eye
• Action:
  • Closes eyelids
  • Assists in pumping tears into the nasolacrimal duct

Orbicularis Oris

• Location: Circular muscle surrounding the mouth
• Action:
  • Closes the mouth
  • Protrudes lips
  • Compresses lips
  • Shapes the lips during speech and eating

Zygomaticus Major

• Location: Diagonally across the cheek (runs from the cheekbone to the corners of the mouth)
• Action: Elevates the corners of the mouth helping in smiling or laughing