The action of the medial pterygoid muscle initiate elevation of the mandible. It also assits the mandible in moving from side to side.
The medial pterygoid muscle inserts onto the medial surface of the ramus and the angle of the mandible.
The V3 (mandibular) branch of the trigeminal nerve (cranial nerve V) innervates the temporalis muscle.
Image by Jessica Fitzgerald. Adapted from an image in the BMS225 handbook.