Twelve pairs of trigeminal nervesCerebral nerveThe fifth pair of brain nerves is one of the mixed brain nerves.The trigeminal nerve is composed of two fiber components.
One is the general somatosensory fibers, whose neuronal cell bodies are located in the trigeminal ganglion composed of pseudounipolar neurons at the impression of the trigeminal nerve in the petrous part of the temporal bone of the middle cranial fossa.The central process of the trigeminal ganglion forms the sensory root of the trigeminal nerve, which enters the brain at the junction of the pontine arm of the brainstem and the base of the pons. The nerve fibers that transmit the sense of touch to the head and face end in the pontine nucleus of the trigeminal nerve, and the nerve fibers that transmit the sense of temperature and pain end in the spinal tract nucleus of the trigeminal nerve.
The other fiber is special visceral motor fiber, which originates from the trigeminal motor nucleus in the special visceral motor nucleus. The special visceral motor fiber components from the trigeminal motor nucleus constitute the trigeminal motor root, which exits the brain from the junction of the pontine arm and the base. The fiber components are added to the mandibular nerve of the third branch of the trigeminal nerve to control the movement of muscles such as masticatory muscles.
2、 Classification
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The peripheral processes of the trigeminal ganglion constitute the three branches of the trigeminal nerve, namely, the Ophthalmic nerve, the Maxillary nerve, and the Mandibular nerve.
（1） Eye contact:
The Eye Channel is a sensory nerve. The fiber component is a kind of general somatosensory fiber. After sending out from the trigeminal ganglion, it penetrates the supraorbital fissure into the orbit, sending out branches such as the frontal nerve, lacrimal gland nerve, and nasociliary nerve, and transmitting general somatosensory information to the head and face skin, conjunctiva, eyeball, and some paranasal sinus mucosa above the eye fissure.
1. The frontal nerve is relatively large, located above the levator palpebrae superioris muscle, and divided into 2~3 branches. The supraorbital nerve is larger, and its branches are distributed on the skin of the top of the forehead through the supraorbital notch.
2. The nerve of lacrimal gland is small and distributed in the lacrimal gland and the skin of the upper eyelid along the lateral wall of the orbit and the upper edge of the lateral rectus muscle to the lacrimal gland.
3. The nasociliary nerve is on the deep side of the superior rectus muscle, passing over the optic nerve and reaching the medial wall of the orbit.The nerve has many branches, which are distributed in the eyeball, sphenoid sinus, ethmoid sinus, lower eyelid, lacrimal sac, nasal mucosa and nasal dorsal skin.
（2） Maxillary nerve:
The maxillary nerve is a sensory nerve, containing general somatosensory fibers. It passes through the lateral wall of the cavernous sinus, passes through the round hole and exits the skull to send out the suborbital nerve, upper alveolar nerve, zygomatic nerve, pterygopalatine nerve, etc. It is distributed in the maxillary teeth, gums, nasal mucosa, etc.
1. The infraorbital nerve enters the orbit through the infraorbital fissure, and then disperses into several branches through the infraorbital groove, the infraorbital canal, and the infraorbital hole, which are distributed on the lower eyelid, the lateral part of the nose, the upper lip, and the cheek skin.In clinical practice, anesthesia is often performed at the infraorbital foramen when maxillary surgery is performed.The infraorbital nerve sends out the anterior branch of the upper alveolar in the infraorbital canal, and the teeth and gums in the anterior part of the upper jaw.When the infraorbital nerve is damaged, the sensation of its innervating area is impaired.
2. The maxillary alveolar nerve is divided into three groups: ① the posterior branch of the maxillary alveolar nerve, which sends out 2-3 branches from the pterygopalatine fossa segment of the maxillary nerve, passes through the back of the maxillary bone to enter the bone, and is distributed in the maxillary sinus, maxillary molars, gums, and buccal mucosa; ②The middle branch of the upper alveolar, which originates from the infraorbital sulcus, is distributed on the maxillary premolars and gums; ③The anterior branch of the upper alveolar, 2~3 branches from the infraorbital canal, is distributed on the maxillary incisors, canines and gums.
3. The zygomatic nerve is relatively small, and it branches out at the pterygopalatine fossa. Together with the infraorbital nerve, it enters the orbit through the infraorbital fissure, passes through the lateral wall of the orbit, and is distributed in the zygomatic skin.If this nerve is damaged, the sensation of its distribution area will be impaired.
（3） Mandibular nerve:
The mandibular nerve is a mixed nerve, which is composed of special visceral motor fibers and general somatosensory fibers. It passes through the foramen ovale and exits the skull, sending out ototemporal nerve, buccal nerve, lingual nerve, inferior alveolar nerve and masticatory muscle nerve. Its motor fibers innervate masticatory muscles, etc;The sensory fibers manage the general sensation of the temporal part, the skin below the cleft mouth, the anterior 2/3 mucosa of the tongue, the mandibular teeth and gums.
3、 Trigeminal nerve injury
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When the trigeminal nerve is injured above the semilunar ganglion: general sensory loss of the affected side's head and face skin, tongue, mouth and nasal mucosa may occur;Corneal reflex disappeared;The masticatory muscles of the affected side were paralyzed, and the mandible deviated to the affected side when opening the mouth.
When the trigeminal nerve is damaged below the semilunar ganglion: each single branch can be injured. When the eye meridian is damaged, the sensory barrier of the skin above the palpebral fissure on the affected side appears, and the corneal reflex disappears;When the maxillary nerve is injured, the sensory disturbance of the affected side's lower eyelid and upper lip skin, maxillary teeth, gums and hard palate mucosa can be reached;When the mandibular nerve is damaged, it can cause the general sensory disturbance of the affected mandibular teeth, gums, 2/3 of the front of the tongue and the mandibular skin, as well as the movement disturbance of the affected masticatory muscles.
