Cranial nerves (gross anatomy) Flashcards
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Olfactory nerve [cranial nerve I] - the paired sensory nerve which carries olfactory information. It’s chemoreceptors are located in the olfactory mucosa and its numerous axons penetrate the cribriform plate through the numerous for foramina of the ethmoid bone to reach the olfactory bulbs of the cerebrum. The tiny axons of the olfactory nerves are all broken on isolated brains, but the olfactory bulbs and tracts can be identified.
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Optic nerve [cranial nerve II] - The paired sensory nerve which carries visual information to the brain. It’s photoreceptors (rods and cones) are located in layer nine of the retina of the eyeball. The optic nerves are the structures extending anteriorly from the optic chiasm. They course through the optic canals of the sphenoid bone and attach to the posterior aspects of the eyeballs.
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Oculomotor nerve [cranial nerve III] - The paired motor nerve which supplies the intrinsic muscles of the eyeball (ciliary muscle and pupillary sphincter muscle) as well as all of the extrinsic muscles of the eye except the lateral recuts and superior oblique muscles. It emerges from the brain in the cleft between the pons and mesencephalon. It then passes through the superior orbital fissure to reach the orbit.
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Trochlear nerve [cranial nerve IV] - The paired motor nerve which innervates the superior oblique muscle. With the exception of the individual fasciculi of the olfactory nerves, it is the smallest cranial nerve and is the only one that attaches to the dorsal (posterior) aspect of the brainstem. The trochlear nerves emerge from the base of the inferior colliculus of the mesencephalon and course around the pons from top to bottom just anterior to the large trigeminal nerves. They accompany the oculomotor nerves through the superior orbital fissure.
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Trigeminal nerve [cranial nerve V] - The paired sensory and motor nerve which is the major nerve for general sensation in the head. It is also the largest cranial nerve (in diameter) and is the only one that emerges from the side of the pons. The trigeminal nerve has 3 large divisions (branches) and each one emerges through a different passageway in the skull. These 3 branches are the ophthalmic nerve, maxillary nerve, and mandibular nerve.
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Ophthalmic nerve - the branch of the trigeminal nerve that courses through the superior orbital fissure to supply general sensory fibers to the eyeball, upper eyelid, and forehead.
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Maxillary nerve - The branch of the trigeminal nerve that courses through the round foramen of the sphenoid bone to supply general sensory fibers to the front of the face (lower eyelid, upper lip, and everything between), and to the upper teeth and gums.
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Mandibular nerve - The branch of the trigeminal nerve that passes through the oval foramen of the sphenoid bone to supply general sensory fibers to the tongue, lower teeth and gums, and lower lip and surrounding tissues. It also supplies motor fibers to the muscles of mastication.
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Abducens nerve [cranial nerve VI] - The paired motor nerve to the lateral rectus muscle of the eye. It emerges from the cleft separating the pons from the medulla oblongata (bulbopontine sulcus) and is transmitted through the skull via the superior orbital fissure.
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Facial nerve [cranial nerve VII] - The paired sensory and motor nerve that supplies motor fibers to the lacrimal, sublingual, and submandibular glands and to the stapedius muscle. The facial nerve carries sensory (taste) fibers from the anterior two-thirds of the tongue. The facial nerve is the middle nerve of the three that emerge from the inferior edge of the pons (in the bulbopontine sulcus). It enters the internal acoustic meatus with the vestibulocochlear nerve but passes on through the skull via the stylomastoid foramen of the temporal bone.
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Vestibulocochlear nerve [cranial nerve VIII] - The paired sensory nerve that functions in hearing and balance. This nerve enters the brain adjacent (and posterior) to the facial nerve as two branches (vestibular and cochlear nerves) partially fused together. The vestibular nerve carries equilibrium sensory impulses destined for the temporal lobe of the cerebral hemispheres. The cochlear nerve carries auditory sensory impulses destined for the temporal lobe of the cerebral hemispheres.
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Glossopharyngeal nerve [cranial nerve IX] - The paired sensory and motor nerve that carries motor fibers to the parotid gland and to the muscles of the pharynx as well as sensory (taste) fibers from the posterior third of the tongue. It emerges as the most anterior part of the 9, 10, 11 triplet of small nerves on the side of the medulla oblongata. The glossopharyngeal nerve passes through the jugular foramen along with the vagus and accessory nerves.
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Vagus nerve [cranial nerve X] - The paired sensory and motor nerve that supplies much of the smooth muscle and glands in the respiratory and digestive organs. It also supplies skeletal muscles in the pharynx and larynx, parasympathetic fibers to the heart, and it is a major sensory nerve for many of the internal organs. The vagus nerves is the largest one attached tot eh side of the medulla oblongata and it is positioned posterior to the glossopharyngeal nerve. It is transmitted through the skull via the jugular foramen. As it follows the esophagus inferiorly, each vagus nerve divides and their anterior and posterior branches anastomose to form the anterior and posterior vagal trunks.
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Accessory nerve [cranial nerve XI] - The paired motor nerve which partially originates from a fiber bundle ascending along the spinal cord. The latter passes up through the foramen magnum of the occipital bone and joins a small fiber bundle from the medulla to make the definitive nerve. It then passes through the skull via the jugular foramen and supplies the trapezius muscle, sternocleidomastoideus muscle, as well as parts of some others.
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Hypoglossal nerve [cranial nerve XII] - The paired motor nerve that passes through the hypoglossal canal of the occipital bone and supplies the intrinsic and extrinsic muscles of the tongue.
