Trigeminal nerve is a mixed nerve. It is the largest of the cranial nerves. It is connected to the lateral aspect of the pons by a large sensory root and a small motor root; the sensory root forms the semilunar ganglion under which the motor root passes forward.
The convex face of the ganglion gives off three branches, the ophthalmic, maxillary and mandibular nerves.
Ophthalmic nerve
- The ophthalmic nerve is purely sensory and leaves the cranium through the foramen orbitorotundum and divides into frontal, lacrimal and naso ciliary branches.
- The frontal nerve emerges from the orbit through the supraorbital canal and supplies the upper eyelid and the skin.
- The lacrimal nerve supplies the lacrimal gland, skin over the temporal fossa, frontal sinus and a long cornual branch that passes below the lateral border of the body of the frontal bone along with the branches of superficial temporal artery and vein to supply the corium of the horn.
- The naso ciliary nerve runs toward the ethmoidal foramen where it divides into the ethmoidal nerve and the infra-trochlear nerve.
- The ethmoidal nerve passes through the ethmoidal foramen into cranial cavity and leaves it through the cribriform plate of ethmoid and supplies the nasal mucous membrane.
- The infratrochlear nerve runs towards the medial canthus and supplies the conjunctiva, lacrimal ducts, lacrimal sac and the third eyelid.
Maxillary nerve
- The maxillary nerve is the largest of the three branches and is also purely sensory like the ophthalmic.
- It emerges out of the cranium through the foramen orbitorotundum runs forward in the pterygopalatine fossa and gives off the following branches.
- zygomatic or orbital branch which runs to the lateral canthus and supplies lower eyelid and skin.
- sphenopalatine nerve that is given off in the pterygopalatine fossa, bears the sphenopalatine ganglion. It divides into
- posterior nasal nerve passes through sphenopalatine foramen to supply the nasal mucous membrane.
- the greater or anterior palatine which runs through the palatine canal and groove to supply hard palate and gums.
- the lesser or posterior palatine which passes downward to supply the soft palate.
- Then the maxillary nerve continues as the infraorbital nerve, which passes through the infraorbital canal, gives off dental branches to the upper cheek teeth, alveolar periosteum and gums, emerges out of the infraorbital foramen and divides into nasal and labial branches to supply nostril and upper lip, respectively.
Mandibular Nerve
- The mandibular nerve is a mixed nerve. Its sensory root arises from the semilunar ganglion soon after it is joined by the motor root. The motor fibres supply only the muscles of mastication. The mixed nerve thus formed leaves the cranium through the foramen ovale, runs downwards between the pterygoids, enters the mandibular foramen of the mandible, runs through the inferior dental canal and gains exit at the mental foramen. Before entering the mandibular canal. It gives off a number of branches in its course.
- Masseteric nerve: Passes through the mandibular notch enters the deep face of the masseter and supplies it.
- Deep temporal: To supply temporalis muscle.
- Buccinator nerve: Passes downward and forward on the medial aspect of temporo mandibular articulation, runs downward in the submucous tissue of the cheek and supplies mucosa of the cheek.
- Pterygoid nerve: Arises in common with the preceding and supplies the pterygoid muscles and branches to tensor palati and tensor tympani.
- Mylohyoid nerve: Passes downward to supply the mylohyoideus muscle and also the anterior belly of digastricus.
- Superficial temporal nerve: Passes backward to the posterior border of the mandible a little below its neck turns outward and then forward under the parotid lymph gland and divides into transverse facial nerve, supplying skin of the cheek and a ventral branch which unites with the dorsal buccal division of the facial nerve. It also gives a branch to parotid salivary gland that conveys postganglionic secretomotor fibres from otic ganglion.
- Lingual nerve:Runs downwards and forward between the ramus of the mandible and medial pterygoid muscle to the root of the tongue, where it divides into a superficial branch, which accompanies the mandibular duct on the deep face of the sublingual gland and supplies the mucous membrane of the tongue and floor of the mouth and a deep branch, which runs between hyoglossus to the tip of the tongue. It supplies the mucous membrane of the anterior two third of the tongue.
- In the course of the mandibular nerve through the mandibular canal,it supplies dental branches to lower cheek teeth, and sends a branch through the incisor canal to supply lower incisors. After emerging out of the mental foramen, the nerve divides into a number of labial filaments to supply the lower lip.