Functions of the medial pterygoid muscle

Abstract Many anatomy textbooks disagree on protrusive and lateral functions of the medial pterygoid muscle. The muscle fibers run obliquely and anteroposteriorly and function during jaw closing, protrusion, and lateral movements. Mandibular movement during protrusion and lateral jaw movement to the contralateral side are described, as well as medial pterygoid muscle action contributing to these movements. Protrusive and lateral isometric muscle tests can identify pterygoid muscle function. Masticatory muscle function correlates closely with muscle fiber direction.