Cranial Nerves

I) – Olfactory N. (plate 113) – F. of Cribform Plate.

1) SVA – Smell – Ant. Olfactory Nucleus in Olfactory Tract.

II) – Optic N. (plate 114) – Optic Canal.

1) SSA – Vision – Lateral Geniculate Nucleus.

III) – Oculomotor N. (plate 115) – Superior Ophthalmic Fissure.

1) GVE – Parasympathetic supply via ciliary ganglia to sphincter pupilae and the ciliary muscle. From Edinger-Westphal Nucleus.

2) GSE – Motor supply to all muscles of the eye except superior oblique and lateral rectus. From Oculomotor nucleus.

IV) – Trochlear N. (plate 115) – Superior Ophthalmic Fissure.

1) GSE – Motor supply to the Superior Oblique Muscle from the Trochlear Nucleus.

V) – Trigeminal N. (plate 116)

V₁) – Ophthalmic N – Superior Ophthalmic Fissure.

1) GSA – Sensory from middle scalp, face down to upper eyelid, part of the nasal mucosa and the paranasal sinuses. Cell bodies in the Trigeminal Nucleus going to Principle Sensor Nucleus in the Spinal Tract.

V₂) – Maxillary N – F. Rotundum.

1) GSA – Sensory to the face from about the lower eyelid to the upper lip, the upper teeth, nasal mucosa, maxillary sinus and mucosa of the anterior palate. Cell bodies in the Trigeminal Ganglion on path the Principle Sensory Nucleus in the Spinal Tract.

V₃) – Mandibular N – F. Ovale.

1) GSA – Sensory to the face from the lower lip down, lower teeth, TMJ, mucosa of the mouth and general sensation from the anterior 2/3 of the tongue. Cell bodies in trigeminal ganglion in their path to the Principle Sensory Nucleus in the Spinal Tract.

2) SVE – Motor to the muscles of the first pharyngeal arch. Muscles of mastication (temporalis, massater, lateral pterygoid and medial pterygoid) Mylohyoid, anterior belly of the digastric, tensor veli palatini and tensor tympani. Fibers originate in the motor nucleus of the trigeminal nerve.

VI) – Abducent N. (plate 115) – Superior Ophthalmic Fissure.

1) GSE – Motor to the lateral rectus muscle. Fibers from the abducent nucleus.

VII) – Facial N. (plate 117) – Passes through internal acoustic meatus to enter the petroustemporal fossa.

1) SVE – Muscles from the second pharyngeal arch that are the muscles of facial expression, stapedius, stylohyoid, posterior belly of the digastric. Fibers come from the motor nucleus of the facial nerve. Exit through the stylomastoid foramen except for the nerve to stapedius that is given off in the petroustemporal fossa.

2) GVE – Parasympathetic supply from the superior salviatory nucleus and branches are given off in the petroustemporal fossa.

a. Greater petrosal nerve synapses in the pterygopalatine ganglion to supply the lacrimal gland. Exits via the superior ophthalmic fissure.

b. The chorda tympani carries parasympathetic fibers that synapse in the submandibular ganglion to supply the submandibular and sublingual glands. Exits via the pterygotympanic fissure.

3) SVA – Chorda tympani carries taste fibers from the anterior 2/3 of the tongue through the pterygotympanic fissure into the geniculate ganglion on the way to the solitary tract nucleus.

4) GSA – Cutanious sensation from the external acoustic meatus. Passes through the external acoustic meatus.

VIII) – Vestibulocochlear N. (plate 118) – carries SSA for hearing and balance from inner ear into vestibuar and cochlear nuclei.

IX) – Glossopharyngeal N. (plate 119) – Exits via the jugular foramen.

1) SVE – Muscle from the third pharyngeal arch, stylopharyngeus. From the nucleus ambiguus.

2) GVE – Parasympathetic supply to the parotid gland from the inferior salviatory nucleus. Carried by the tympanic nerve to the tympanic plexus to the lesser petrosal nerve to the otic ganglion and then rides with the auriculotemporal nerve (of V₃) to the parotid gland.

3) GVA – Sensory from the carotid body and sinus. Cell bodies in the superior ganglion on their way to the solitary tract nucleus. This is the sensory branch of the vagal reflex.

4) GSA – General sensation to the posterior 1/3 of the tongue, the medial side of the tympanic membrane and the mucosa of the inner ear. Inferior ganglion to spinal tract nucleus.

5) SVA – Taste from the posterior 1/3 of the tongue. Through the inferior ganglion to the spinal tract nucleus.

X) – Vagus N. (plate 120) – Exits via the jugular foramen.

1) SVA – Taste from the root of the tongue and the epiglottis. Inferior ganglion enroute to solitary tract nucleus.

2) GSA – Sensory to the external ear, external surface of the tympanic membrane, epiglottis and roots of tongue. Travels via the inferior nucleus to the spinal tract.

3) GVA – Sensory from the pharynx, larynx, thoracic and abdominal viscera and the aortic body. Cell bodies in the superior and inferior ganglia on the way to the solitary tract nucleus.

4) GVE – Parasympathetic supply to cardiac muscle and smooth muscles of arteries, respiratory and GI tract.

5) SVE – Muscles of palate (except tensor veli palatini), muscles of pharynx (except for stylopharyngeus) and muscles of larynx. From the nucleus ambiguus.

The vagus gives off three branches that supply the laryngeal region which are of great importance on.

1) Internal laryngeal branch that runs with the superior laryngeal artery and innervates the true and false vocal folds and the mucosa of the larynx above the folds.

2) External laryngeal branch that runs with the superior thyroid artery and innervates the criocthyroid muscle.

3) Recurrent branch of the laryngeal nerve that recurs around the subclavian artery on the right and the ligamentum arteriousm (or aorta) on the left. It runs with the inferior thyroid artery and innervates all muscles of the larynx other then the criocthyroid.

XI) Accessory N. (plate 121)

1) Cranial accessory nerve – fibers come from the nucleus ambiguus and join the vagus nerve around the jugular foramen.

2) Spinal accessory nerve – fibers come from the spinal cord that go up to the brainstem and exit via the jugular foramen to provide GSE (motor) innervation to the trapezius and sternocleidomastoid muscles.

XII) Hypoglossal N. (plate 122) – exits via the hypoglossal canal.

1) GSE to al muscles of the tongue except for the platoglossus. Fibers come from the hypoglossal nucleus.

Cervical Plexus (C1-4)

1) Fibers of C1 via the hypoglossal nerve supply the geniohyoid and thyrohyoid muscles.

2) Ansa cervicalis

a. The superior branch (dencendens hypoglossus) primarily carry fibers from C1 and innervate the superior belly of the omohyoid, sternohyoid and sternothyroid.

b. The inferior branch primarily carries fibers from C2-3 and innervates the inferior belly of the omohyoid.

3) There are six sensory nerves from the cervical plexus.

a. Sensory supply from the sternocleidomastoid to C2,3.

b. Lesser occipital nerve (C2,3).

c. Greater auricular nerve (C2,3).

d. Transverse cervical nerve (C2,3).

e. Sensory supply from the trapezius (C3,4).

f. Medial, intermediate and lateral supraclavicular nerves (C3,4).

4) The phrenic nerve gets some of it’s supply from the cervical plexus and some from the brachial plexus as it’s roots are C3,4,5.

Sympathetic Supply

Sympathetic to the head and neck is via three cervical sympathetic ganglia in the sympathetic ganglion chain. Sympathetic supply only exits the spinal cord so it supply the head and neck it must go up via the paravetebral ganglion chain. Sympathetic fibers travel from the ventral roots to the chain in the white rami communicants. They then synapse in that ganglion or travel up or down to the one they want to synapse in. The postganglionic fibers travel via gray rami communicants back to the ventral roots where they go to the structures they are to innervate.

The preganglionic communicants are white because preganglionic sympathetic fibers are mylenated. Mylin is a fatty substance and is white. Postganglionic fibers are not mylenated therefore appearing gray.

There are three sympathetic ganglia in the cervical region.

1) Superior cervical ganglion – Is located at the level of C2,3 and distributes fibers to C1,2,3,4.

2) Middle cervical ganglion – Is located at the level of C5 and distributes fibers to C5,6.

3) Interior cervical ganglion – Is located at the level of C7 and distributes postganglionic fibers to C7,8. It is often joined with the ganglion of T1 and called the stellate ganglion.

Return to Semester Two Goodies

Return to The Unofficial Ross Page