The lateral pterygoid muscle has a triangular shape, with two heads; superior and inferior. It is active during mastication and mandibular movements - including protrusion (forward movement of the mandible), abduction (depression of the mandible), mediotrusion (mandibular condyle movement towards the midline). It works particularly during speaking, singing, and clenching.
It has horizontally orientated muscle fibers, and thus is the major protractor of the mandible. Acting bilaterally, the lateral pterygoids protract the mandible, pushing the jaw forwards. Unilateral action produces the ‘side to side’ movement of the jaw.
The lateral pterygoid is the only muscle of mastication that assists in depressing the mandible (opening the jaw). At the beginning of this action it is assisted by the digastric, mylohyoid and geniohyoid muscles.
Functionally, the muscle is analogous to the temporalis muscle. The fan-shaped temporalis muscle exhibits a continuous range of anteroposterior movements, while the lateral pterygoid muscle exhibits a range of mediolateral and supero inferior movements.
The medial pterygoid muscle, a major elevator of the jaw is a square-shaped masticatory muscle, located on the medial aspect of the lower jaw bilaterally. The medial pterygoid assist in elevation and protrusion of the jaw. It also has a role in the horizontal movements of the jaw.
Rathee M, Jain P. Anatomy, Head and Neck, Lateral Pterygoid Muscle. 2021 Oct 29. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 31747206.
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