The fifth cranial nerve, known as the trigeminal nerve, is involved with both sensation to the face as well as the muscles of mastication.  Both the motor and sensory portions of the trigeminal nerve emerge from the lateral aspect of the pons.  The nerve travels out to the Gasserian ganglion, from where three branches or divisions of the nerve are given off.  The ophthalmic division supplies sensation to the forehead and cornea.  This division is responsible for the corneal reflex (when something touches the cornea, the eye reflexively blinks shut).  The maxillary division supplies the cheek, and the mandibular dividion,  the jaw.  A division of the mandibular  branch supplies the muscles of mastication (masseter, pterygoids and temporalis), and also supplies sensation to the cheek and gums through the buccal nerve.  The lingual branch helps in supplying taste to the anterior two thirds of the tongue.