Hygiene Atlas

Atlas · Plate I · Head and Neck Anatomy · 03

Muscles of mastication and expression

Four muscles of mastication, all supplied by V3, move the mandible. The masseter, temporalis and medial pterygoid close the jaw, while the lateral pterygoid protrudes it and helps open. The muscles of facial expression, including the buccinator and orbicularis oris, are all supplied by the facial nerve (CN VII). Palpate the masseter on both sides during the extraoral exam.

High-yield facts · 10

  1. Muscles of mastication: masseter, temporalis, medial pterygoid, lateral pterygoid; all are supplied by V3.S45
  2. Elevators (closers): masseter, temporalis, medial pterygoid.T4
  3. The inferior head of the lateral pterygoid is the main protruder and helps open; one side alone moves the jaw to the opposite side.T4
  4. The posterior fibers of the temporalis retract the mandible.T4
  5. The masseter is the strongest and most superficial mastication muscle; palpate it bilaterally during the EO exam.T4
  6. Muscles of facial expression are all supplied by CN VII.T4
  7. The buccinator forms the cheek, keeps food on the occlusal table and is pierced by the parotid duct.T4
  8. The orbicularis oris closes the lips; the mentalis raises the chin and protrudes the lower lip.T4
  9. The digastric (anterior belly V3, posterior belly VII) and mylohyoid (V3) are suprahyoid muscles that help depress the mandible.T4
  10. The mylohyoid forms the floor of the mouth; infection of the mandibular molars (apices below its line) spreads to the submandibular space.T4

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