CRANIAL NERVES

Describe the origin, course, branches and distribution of major cranial nerves. Describe applied anatomy.

Origin of Cranial Nerves

Course of Cranial Nerves

I. Olfactory Nerve (CN I)

Origin: Olfactory epithelium of the nasal cavity
Course: Passes through the cribriform plate and enters the cranial cavity
Branches: None
Distribution: Relays sensory information from the nasal cavity to the olfactory bulb

II. Optic Nerve (CN II)

Origin: Retina of the eye
Course: Passes through the optic canal and enters the optic chiasm
Branches: None
Distribution: Relays visual information to the optic chiasm and higher visual centers

III. Oculomotor Nerve (CN III)

Origin: Interpeduncular fossa of the midbrain
Course: Passes through the cavernous sinus and exits through the superior orbital fissure
Branches: Superior and inferior branches
Distribution: Supplies the extraocular muscles (except the superior oblique), levator palpebrae superioris, ciliary muscles and the parasympathetic fibers to the sphincter pupillae and ciliary ganglion

IV. Trochlear Nerve (CN IV)

Origin: Dorsal aspect of the cerebral peduncle
Course: Passes through the cavernous sinus and exits through the superior orbital fissure
Branches: None
Distribution: Supplies the superior oblique muscle of the eye

V. Trigeminal Nerve (CN V)

Origin: Lateral surface of the pons
Course: Passes through the Meckel's cave and exits through the foramen ovale
Branches: Ophthalmic, maxillary and mandibular divisions
Distribution: Sensory to the face, motor to the muscles of mastication and parasympathetic to the lacrimal gland

VI. Abducens Nerve (CN VI)

Origin: Pons
Course: Passes through the cavernous sinus and exits through the superior orbital fissure
Branches: None
Distribution: Supplies the lateral rectus muscle of the eye

VII. Facial Nerve (CN VII)

Origin: Lateral surface of the pons
Course: Passes through the internal auditory meatus and exits through the stylomastoid foramen
Branches: Branches to the stapedius and stylohyoid muscles, chorda tympani and facial branches
Distribution: Sensory to the taste buds of the anterior two-thirds of the tongue, motor to the muscles of facial expression and parasympathetic to the submandibular and sublingual glands

VIII. Auditory Nerve (CN VIII)

Origin: Cochlear nuclei of the pons
Course: Passes through the internal auditory meatus and exits through the internal auditory meatus
Branches: None
Distribution: Relays auditory information from the cochlea to the cochlear nuclei

IX. Glossopharyngeal Nerve (CN IX)

Origin: Medulla oblongata
Course: Passes through the jugular foramen and exits through the jugular foramen
Branches: Tympanic and carotid branches
Distribution: Sensory to the posterior one-third of the tongue and pharynx, motor to the stylopharyngeus muscle and parasympathetic to the parotid gland

X. Vagus Nerve (CN X)

Origin: Medulla oblongata
Course: Passes through the jugular foramen and exits through the jugular foramen
Branches: Various branches to the pharynx, larynx and abdominal organs
Distribution: Sensory to the pharynx and larynx, motor to the muscles of the pharynx and larynx and parasympathetic to various abdominal organs

XI. Spinal Accessory Nerve (CN XI)

XII. Hypoglossal Nerve (CN XII)

Origin: Medulla oblongata
Course: Passes through the hypoglossal canal and exits through the hypoglossal canal
Branches: None
Distribution: Motor to the muscles of the tongue

Applied Anatomy

Cranial nerves control various functions such as vision, hearing, taste, smell, facial expression and swallowing
Damage to cranial nerves can result in various neurological deficits
Knowledge of cranial nerves is essential for various medical and surgical procedures.