Which muscle action relates to the Inability to close the lip?

Orbicularis oris- orbicularis oris is a muscle of facial expression. it surrounds the lips, and allows for pursing of the lips. it is innervated by the buccal branch of the facial nerve. the anterior belly of the digastric and mylohyoid both help elevate the hyoid bone and depress the mandible. they are both innervated by a branch of the mandibular division of the trigeminal nerve (v3). platysma and zygomaticus major are both muscles of facial expression, innervated by the facial nerve. platysma draws the corners of the mouth down and aids in depressing the mandible; zygomaticus major elevates and draws the corners of the mouth laterally.