Which muscle depresses the mandible and assists in opening the mouth?

• A. Lateral Pterygoid
• B. Suprahyoid Muscles
• C. Anterior Digastric
• D. Mylohyoid

Answer: (A)

Opening the mouth relies on muscles that pull the mandible downward, and the lateral pterygoid is the one that directly handles this movement in a way that also sets up the jaw for opening. The inferior head of the lateral pterygoid attaches to the neck of the mandible and when it contracts it pulls the condyle downward and forward. This not only lowers the mandible but also pulls the articular disc anteriorly, allowing the condyle to translate along the articular eminence so the mouth can open smoothly. In contrast, the suprahyoid muscles (like the digastric, mylohyoid, and geniohyoid) help open the mouth more by elevating the hyoid and floor of the mouth and stabilizing the jaw in swallowing or speech; their role in directly depressing the mandible is secondary. Therefore, the lateral pterygoid best fits both parts of the question: it depresses the mandible and actively assists in opening the mouth by coordinating with the TMJ mechanics.