The temporalis muscles
The temporalis muscle (temporal muscle) is a broad fan shaped muscle on each side of the head covering much of the temporal bone. It is not facial expression muscle, but one of the mastication muscles (chewing muscles). It is attached to the mandible (jaw) and to the skull’s temporal bone, or temporal fossa. It is one of the muscles involved in jaw movement (lift the jaw and retract the jaw) and is the most powerful chewing muscle of the temporomandibular joint. You can see and feel the muscle contracting while the jaw is clenching and unclenching. The muscle is innervated by a branch of trigeminal nerve.
The masseter muscles
One of the strongest chewing muscles is masseter muscle. It consists of two heads: superficial head starts from the maxillary process of the zygomatic bone and the anterior two thirds of the inferior border of the zygomatic arch and inserts into the angle of the mandible and inferior half of the lateral surface of the ramus of the mandible; the deep head starts from the posterior third of the lower border and from the whole of the medial surface of the zygomatic arch and inserts into the upper half of the ramus of the mandible. This muscle involves jaw movement.
