Interior head of both side: pull the condyle forward---->open the jaw;
Superior head of lateral pterygoid: when the distance btw condyle and mandibular fossa suddenly increase and the internal pressure of articular cavity suddenly decreases (happens during power stroke), the superior head pull the articular disc forward and medially so the thicker posterior band of articular disk will occupy the increased space. By this way, the articular dic can stay stable in the joint cavities.
