Which muscle is primarily responsible for jaw closure?

The masseter muscle is primarily responsible for jaw closure because it is one of the main muscles involved in the chewing process, specifically in elevating the mandible to bring the upper and lower jaws together. This powerful muscle originates from the zygomatic arch and inserts into the angle and ramus of the mandible, allowing it to exert significant force when contracted. The masseter is synergistic with other muscles involved in mastication, but its primary function focuses on closing the jaw.

While the temporalis muscle also plays a role in elevating the jaw, particularly during a more rapid or powerful bite, it is not the primary muscle solely responsible for closure. The pterygoid muscles contribute to lateral movements and also assist in closing the jaw, but they are more involved in complex movements of the jaw rather than the primary action of closure. The buccinators muscle is primarily involved in keeping food positioned between the molars while chewing, rather than directly contributing to the closure of the jaw. This anatomical and functional understanding highlights why the masseter is recognized as the main muscle for jaw closure.