Which muscle is primarily responsible for closing the jaw?

• A. Lateral pterygoid
• B. Masseter
• C. Digastric
• D. Buccinator

Answer: (B)

Closing the jaw is about lifting the mandible to bring the teeth together. The muscle that does this most powerfully is the masseter. It runs from the cheekbone to the lower jaw, and when it contracts it elevates the mandible to close the mouth, providing the strongest bite. It can also help protrude the jaw a bit, aiding in biting force.

Other muscles have different roles: the lateral pterygoid helps with opening the jaw and moving the jaw forward, the digastric assists in opening the jaw, and the buccinator mainly tightens the cheek and helps keep food between the teeth but doesn’t close the jaw. (The temporalis and medial pterygoid also contribute to closing, but among the options, the masseter is the primary closing muscle.)