The trigeminal nerve is a mixed nerve, the fifth pair of cerebral nerves and the thickest nerve in the face, containing both general somatic sensory and special visceral motor fibers. It innervates the sensory and masticatory muscles of the face, mouth, and nasal passages, and transmits sensory messages from the head to the brain. This nerve is divided into two parts, the larger part is responsible for sensations of pain, temperature and touch in the face; the smaller part is responsible for the chewing action when eating. The large sensory nerve is divided into three branches: the first branch is called the ophthalmic branch, mainly responsible for the skin above the eye fissure, mucous membrane sensation, such as frontal skin, lid conjunctiva, cornea and other sensations. The second branch is called the maxillary branch, which is responsible for the sensation of the skin and mucous membranes between the eyes and the mouth, such as the sensation of the buccal area, the maxillary skin, the mucous membranes of the nasal cavity, the upper part of the mucous membranes of the oral cavity and the upper teeth. The third branch is called the mandibular branch, which is in charge of the sensation of the skin and mucous membranes below the mouth, such as the skin of the mandible, the mucous membranes of the lower part of the oral cavity and the sensation of the lower teeth. The trigeminal nerve is the thickest nerve in the face, and its motor portion runs from the junction of the pontine bridge and the pontine arm. The motor part of the trigeminal nerve runs from the junction of the pontine bridge and the pontine arm of the brain, and then merges into the mandibular nerve, which passes out of the cranium through the foramen ovale, and the cytosolic body of the sensory part of the trigeminal nerve forms the trigeminal ganglion, which is situated at the tip of the temporal bone.