Which statement is true regarding the muscles of mastication?

The muscles of mastication play a crucial role in the mechanics of jaw movement and are essential for the process of chewing. These muscles include the masseter, temporalis, medial pterygoid, and lateral pterygoid, which work in concert to facilitate the opening, closing, and lateral movement of the jaw. The correct statement emphasizes that these muscles are integral to jaw movements, enabling actions like biting, grinding, and chewing food effectively.

The other statements do not accurately reflect the role and function of the muscles of mastication. While facial expressions are influenced by various muscles, they are primarily controlled by different facial muscles rather than those specifically involved in mastication. Additionally, the muscles of mastication indeed impact the functionality of the temporomandibular joint (TMJ), as their coordinated contractions are critical for smooth and efficient jaw movement. Lastly, the facial nerve primarily innervates the muscles responsible for facial expressions, whereas the muscles of mastication are primarily innervated by the mandibular branch of the trigeminal nerve. Thus, option B is the only accurate statement regarding the muscles of mastication.