What is the primary action of the medial pterygoid muscle?

What is the primary action of the medial pterygoid muscle?

• A. Elevates mandible and laterally deviates it to the opposite side
• B. Protracts mandible
• C. Depresses mandible
• D. Elevates mandible

Answer: (A)

Medial pterygoid helps close the jaw by elevating the mandible, and it can also produce side-to-side movement. When both sides contract, it elevates the mandible to bite down. When it contracts on one side, it not only elevates but also pulls the mandible toward the opposite side, which is why its unilateral action contributes a contralateral deviation. This combination—elevation with contralateral deviation—best captures what this muscle does during chewing. Protracting the mandible is mainly the job of the lateral pterygoid, not the medial pterygoid. Depressing the mandible isn’t a primary action of this muscle, and elevating the mandible alone omits the important side-to-side component that occurs with unilateral contraction.

Medial pterygoid helps close the jaw by elevating the mandible, and it can also produce side-to-side movement. When both sides contract, it elevates the mandible to bite down. When it contracts on one side, it not only elevates but also pulls the mandible toward the opposite side, which is why its unilateral action contributes a contralateral deviation. This combination—elevation with contralateral deviation—best captures what this muscle does during chewing.

Protracting the mandible is mainly the job of the lateral pterygoid, not the medial pterygoid. Depressing the mandible isn’t a primary action of this muscle, and elevating the mandible alone omits the important side-to-side component that occurs with unilateral contraction.