Lateral pterygoid muscle is one of the four classical muscles of mastication including masseter, temporalis and medial pterygoid. Main function of lateral pterygoid muscle is to open the mouth or lower the mandible at temporomandibular joint. The upper/superior head of lateral pterygoid muscle originates from the infratemporal surface and infratemporal crest of the greater wing of sphenoid bone, and lower/inferior head from outer or lateral surface of lateral pterygoid plate. Inferior head inserts into the pterygoid fovea at neck of condylar process of the mandible; upper/superior head inserts into articular disc and fibrous capsule of temporomandibular joint. The mandibular division of trigeminal nerve, specifically nerve to lateral pterygoid nerve, innervates the lateral pterygoid muscle. The primary function of the lateral pterygoid muscle is to pull the head of the condyle out of the mandibular fossa along the articular eminence to protrude the mandible. A concerted effort of the lateral pterygoid muscles helps in lowering the mandible and open the jaw whereas unilateral action of a lateral pterygoid produces contralateral excursion (a form of mastication), usually performed in concert with the medial pterygoids. Unlike the other three muscles of mastication, the lateral pterygoid is the only muscle of mastication that assists in lowering/depression of the mandible (opening the jaw). At the beginning of this action it is assisted by the digastric, mylohyoid and geniohyoid muscles.

Keywords: Lateral Pterygoid Muscle; Muscle of Mastication; Temporomandibular Joint.