This is the fifth(V) cranial nerve. It is the largest of the cranial nerves, which supplies sensory branches to the face, the greater part of the scalp, teeth, oral and nasal cavities, and motor supply to masticatory & some other muscles. It also contains proprioceptive nerve fibers from the masticatory and probably the extraocular muscles. because
Trigeminal nerve derives its name from the fact that it divides into three large nerves, ie, because
- Ophthalmic because
These emerge separately from the cranial cavity.
Trigeminal Nerve Nuclei
The sensory trigeminal nerve nuclei are the largest of the cranial nerve nuclei. Extend through the whole of the midbrain, pons and medulla, and into the high cervical spinal cord. The nucleus is divided into three parts, from rostral to caudal (top to bottom):
- The mesencephalic nucleus because
- The chief sensory nucleus (main sensory nucleus)
- The spinal trigeminal nucleus because
- Midbrain therefore
- Upper pons therefore
- From pons to the C2 segment of the spinal cord
- Movement of mandible therefore
- Innervates muscles of mastication & tensor tympani & tensor palatini
- Proprioceptive: muscles of mastication, face, eye Touch & pressure from skin & mucous membrane of the facial region
- Pain & temperature of the face
Intracranial Course Of Trigeminal Nerve
It emerges from the ventral surface of the pons near its upper border, at the junction of the pons with the middle cerebellar peduncle and consists of two roots
- Larger posterolateral sensory root because
- Smaller anterosuperior motor root because
Fibers in the sensory root are axons of cells in the trigeminal or semilunar ganglion. The neurons of the unipolar cells in the trigeminal ganglion divide into Peripheral and Central branches. The peripheral branches being grouped into ophthalmic and maxillary nerves and sensory part of the mandibular nerve. The central branches constitute the fibers of the sensory root running posteromedially under the superior petrosal sinus and tentorium cerebelli to enter the pons. because
On entering the pons, the fibers of the sensory root divide into ascending and descending branches and the others reach without any division. The descending fibers from the spinal tract of the trigeminal nerve which is a bundle of the sensory fibers of the trigeminal nerve descend through the neurons on the spinal trigeminal nucleus with collaterals. The spinal tract carries sensory fibers from the trigeminal area into the reflux zone of the neck muscles. because
The fibers which end in the nucleus, caudal to the fourth ventricle are principally concerned with the sensations of pain and temperature from the trigeminal area, but the spinal tract and the nucleus also receive fibers of general sensation from other cranial nerves entering the medulla oblongata through it, notably glossopharyngeal and vagus nerves. In the spinal tract, the ophthalmic fibers are ventral and descend to the level of the lower limit of the first cervical spinal segment. Maxillary fibers are central and extend below the medulla oblongata while mandibular fibers extend only up to mid-medullary level.
- Sensory root therefore
- Motor root therefore
It is attached to the lateral part of pons by its two roots – sensory and motor roots • Sensory root arises from semilunar ganglion located in the meckles cavity.
Motor Root Of Trigeminal Nerve
Motor root arises separately from the sensory root, originating in the main nucleus with pons and medulla oblongata. At the sensory (semilunar) ganglion, the motor root passes in a lateral and inferior direction under the ganglion towards the foramen ovale, through which it leaves middle cranial fossa, along with the sensory root of the mandibular nerve. Just after leaving the skull, the motor root unites with the sensory root of the mandibular division to form a single trunk. because
Motor Nucleus Motor Root Of Mandibular Nerve
Muscles of mastication supply tensor tympani masseter, tensor palatini, lateral & medial pterygoid temporalis. CNS motor root supplies the anterior belly of digastric and mylohyoid.
Sensory Root Of Trigeminal Nerve
Sensory root fibers comprise of the central processes of ganglion cells located in trigeminal ganglion (or semilunar / Gasserian ganglion). There are two ganglia, one innervating each side of the face. They are located in Meckel’s cave. Sensory root fibers enter the concave portion of the ganglion and the three sensory divisions of trigeminal nerve exit from the convexity.
Sensory Root General Somatic Afferents
These fibers supply Face, Scalp, Teeth, Gingiva, Oral, Nasal, Cavities, Paranasal sinus, Conjunctiva, and Cornea. Pain, Temp, Light touch Touch, Pressure Proprioception, Trigeminal ganglion Bypasses, Trigeminal ganglion Sensory root. Spinal nucleus and Principal sensory nucleus Mesencephalic. therefore
Types of Fibers
- The Ophthalmic Nerve because
- The Lacrimal Nerve because
- The Frontal Nerve because
- The Supra-Orbital Nerve
- The Naso-Ciliary Nerve because
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