The Cranial Nerves

The Olfactory Nerve, or First Cranial Nerve, is the pathway taken by Olfactory impulses from the Nasal mucosa to the Brain.

The Olfactory Tract connects the Olfactory Bulb with the Olfactory Tubercle, where it divides into a Medial and Lateral Olfactory Tract.

The Optic Nerve, or Second Cranial Nerve, lies just Posterior and Inferior to the Medial Olfactory Tract. It carries information from the Eye for Vision and Ocular Reflexes.

The Third Cranial Nerve, or Oculomotor Nerve arises at the Ventral aspect of the MesenCephalon and transverses through the Cavernous Sinus to the Orbit.

It supplies all the Intrinsic Ocular Muscles and all Extrinsic Ocular Muscles except for the Lateral Rectus and Superior Oblque. The ParaSympathetic Fibers from this Nerve innervate the Ciliary Muscle of the Lens and the Sphincter Muscle of the Pupil.

The Fourth Cranial Nerve, or Trochlear Nerve, supplies only the Superior Oblique Muscle of the Eye, and it arises just below the Inferior Quadrigeminal Bodies of the BrainStem.

It emerges from the Posterior aspect of the BrainStem and passes around the Lateral side of the Cerebellar Peduncle into the Margin of the Tentorium and into the Cavernous Sinus, where it goes to the Orbit.

The Fifth Cranial Nerve, or Trigeminal Nerve, is the Largest Cranial Nerve, and it carries Fibers that give Sensation to the Face and Motor Fibers to the Muscles of Mastication. It exits from the BrainStem through the AnteroLateral surface of the Pons.

The Sixth Cranial Nerve, or Abducent Nerve, supplies the Lateral Rectus Muscle of the Eyeball and issues from the Brain at the Inferior border of the Pons, just above the Pyramid of the Medulla Oblongata.

The Seventh Cranial, or Facial Nerve, consists of two parts:

  • The Motor Root, which supplies the Superficial Muscles of the Scalp, Face, and Neck
  • A smaller Sensory Root, which contains the Afferent Taste Fibers for the Anterior two thirds of the Tongue and the Afferent ParaSympathetic Fibers for supply of the Lacrimal and Salivary Glands
The Facial Nerve arises from the Lateral aspect of the Ponto-Medullary junction.

The Auditory Nerve, or Eighth Cranial Nerve, is entirely Sensory, and consists of Vestibular and Cochlear divisions.

The Glossopharyngeal, or Ninth Cranial Nerve is a Mixed Nerve consisting of an Afferent part, which supplies the Pharynx and Tongue and the Carotid Sinus and Body.

The Efferent part supplies the Stylopharyngeus Muscle. It arises from the Medulla Oblongata by five or six Rootlets attached to the side of the Medulla Oblongata, close to the Facial Nerve.

The Vagus, or Tenth Cranial Nerve is also a Mixed Nerve, which contains a large number of ParaSympathetic Fibers and passes through the Neck and Thorax into the Abdomen. It supplies Afferent Fibers chiefly to the Pharynx, Esophagus, Stomach, Larynx, Trachea, and Lungs.

It's attached by numerous Rootlets to the side of the Medulla Oblongata, in series with the Accessory Nerve below and the Glossopharyngeal Nerve above. The Rootlets unite to form a Single Tract, which exits from the Cranial Cavity through the Jugular Foramen.

The Accessory Nerve, or Eleventh Cranial Nerve, consists of Bulbar and Spinal portions. It arises in series with the Vagus and Glossopharyngeal Nerve and controls Motor Function of the Sternomastoid and the Trapezius Muscles.

The Twelfth Cranial Nerve, or Hypoglossal Nerve, is a predominantly Efferent Nerve that supplies all the Muscles of the Tongue, both Intrinsic and Extrinsic, except the Palatoglossus Muscle.

It arises from numerous Rootlets from the Anterior portion of the Medulla Oblongata. The Rootlets are arranged in double bundles and unite in the Anterior Condylar Canal, where they emerge from the Cranial Cavity.

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