Also known as the trigeminal nerve, nervus trigeminus, and the trifacial nerve. It is the chief sensory nerve of the face and the motor nerve of the muscles of mastication. Its origin is in the mesencephalon and in the ponsextending down into the cervical portion of the spinal cord. It emerges by two roots, the sensory root and the motor root., from the lateral portion of the surface of the pons and enters a cavity of the dura mater, the cavum trigeminale (of Meckel), at the apex of the petrous portion of the temporal bone. From there the sensory root expands to form the trigeminale (Gasserian) ganglion and branches into the the orphthalmic division, the maxillary division, and the mandibular division.