TRIGEMINAL NERVE ANATOMYThe trigeminal nerve is rather large by comparison. It is considered a mixed nerve, and its origins for motor innervation can be traced to the nuclei in the pons. The sensory innervation can be traced to the nuclei in the pons, the midbrain, and the medulla oblongata. From the anterolateral portion of the pons, the origins of the two individual roots of the trigeminal nerve can be located.
TRIGEMINAL NERVE STRUCTUREThe larger of the two tracks into a swollen portion known as the semilunar ganglion, or alternatively the trigeminal ganglion. This location can be found along the temporal bone, more specifically, in the depression within the bone along the inner surface of the petrous segment of this bone.
The trigeminal ganglion bears three large nerves. The ophthalmic nerve can be traced along the superior orbital fissure after passing through the orbit. The maxillary nerve can be traced passing through the foramen rotundum. The third nerve, the mandibular nerve, follows a line through the foramen ovale.
Where the mandibular nerve passes through the foramen ovale, it is joined by the smaller motor root and motor root fibers of the trigeminal nerve. These are specifically targeted to serve the motor function of the muscles of the mastication and specified muscles of the floor of the mouth.
TRIGEMINAL NERVE DIAGRAM
Image: Trigeminal Nerve
The mandibular nerve relays impulses which provide motor signals to the trigeminal ganglion. Theses impulses command contraction of the muscles of mastication. Included in these muscles would be the masseter, the mylohyoid, the lateral and medial pterygoids, the temporalis, and the anterior segment or “belly” of the digastric muscle.
The trigeminal nerve is a mixed nerve, with a strong emphasis on the sensory capabilities over the motor capabilities. There are three sensory nerves of the main trigeminal nerve that are solely responsible for registering pain, temperature sensation, and touch as they apply to the facial area.
TRIGEMINAL NERVE FUNCTIONSOne of these nerves, the ophthalmic nerve, is responsible for registering sensation related impulses from the scalp, upper eyelid, lacrimal gland (also known as the tear gland,) the upper mucosa of the nasal cavity, the forehead skin, the eyeball’s surface, and the side of the nose.
The maxillary nerve is thus responsible for registering sensation as it relates to the cheek skin, the lower eyelid, the upper lip, the lateral and inferior mucosa of the nasal cavity, the teeth and gums of the upper half of the mouth, and the palate with some segments of the pharynx.
The mandibular nerve fibers are responsible for the transmission of sensation as it relates to the lower gums and teeth, mucosa of the mouth, the anterior two thirds of the tongue although it does not transmit taste, the lower facial region, and the auricle of the ear. Any damage received by the mandibular nerve constricts the individual’s ability to chew and manipulate the mouth. Damages to the trigeminal nerve are likely to result in at least some partial paralysis or lack of sensation to their assigned areas.