Which muscle is primarily responsible for mastication?

The muscle primarily responsible for mastication, which is the process of chewing, is the masseter. The masseter muscle is located in the jaw and plays a crucial role in closing the mouth and elevating the mandible, allowing for the grinding and tearing of food. Its strength and position make it one of the most powerful muscles involved in the chewing process.

The temporalis muscle, while also involved in mastication, primarily assists with elevation and retraction of the mandible. The buccinator muscle aids in keeping food positioned between the teeth during chewing but does not directly cause the movement of the jaw. The orbicularis oris is involved in movements of the lips, such as kissing or puckering, but it does not participate in the process of chewing itself. Thus, the correct answer is grounded in the masseter's key role in the physical mechanics of mastication.