Muscle which helps in opening of the mouth:

Lateral PterygoidThe primary function of the lateral pterygoid muscle is to pull the head of the condyle out of the mandibular fossa along the aicular eminence to protrude the mandible.A conceed effo of the lateral pterygoid muscles acts in helping lower the mandible and open the jaw whereas unilateral action of a lateral pterygoid produces contralateral excursion, usually performed in conce with the medial pterygoidsUnlike the other three muscles of mastication, the lateral pterygoid is the only muscle of mastication that assists in depressing the mandible (opening the jaw).At the beginning of this action it is assisted by the digastric,mylohyoid and geniohvoid muscles.