Which action is primarily performed by the masseter muscle?

• A. Elevation of the mandible with some protraction
• B. Depression of the mandible
• C. Protraction of the mandible
• D. Lateral deviation of the mandible

Answer: (A)

Masseter is a powerful jaw elevator. When it contracts on both sides, it raises the mandible to close the mouth. Its fibers, especially the anterior ones, can also pull the mandible forward a bit, contributing to a small amount of forward movement (protraction). Depression of the mandible is not the primary action of the masseter—that opening motion is produced by gravity plus other muscles that depress the jaw. Lateral deviation is mainly a result of unilateral action of the pterygoid muscles and, to some extent, the temporalis, rather than the masseter. So the description that matches its primary role plus a bit of forward movement is elevation with some protraction.