Oculomotor, Trochlear, and Abducent Nerves: Schema Anatomy
1. Ciliary ganglion
2. Short ciliary nerves
3. Inferior division of oculomotor
nerve
4. Pterygopalatine ganglion
5. Abducent nerve (CN VI)
6. Ophthalmic nerve (CN V1)
7. Oculomotor nerve (CN III)
8. Trochlear nerve (CN IV)
Comment: This schema shows the motor innervation to the
extra-ocular muscles (from CN III, CN IV, and CN VI) and the autonomic fibers.
Parasympathetic fibers arise in the brainstem and course with the oculomotor
nerve to the ciliary ganglion.
Postganglionic parasympathetics
innervate the ciliary muscle (which accommodates the lens) and the sphincter
muscle of the pupil.
Sympathetic fibers that synapse in the
superior cervical ganglion send postganglionic fibers to the dilator muscle of
the pupil.
Sensory innervation to the orbit arises
from the ophthalmic division of the trigeminal nerve.
Clinical: Unilateral damage to the oculomotor nerve (CN III) can paralyze the 4 extra-ocular muscles innervated
by this nerve (superior, medial, and inferior rectus muscles and inferior
oblique muscle) and the levator palpebrae superioris muscle of the upper
eyelid, causing ophthalmoplegia and ptosis (drooping of the eyelid).
Additionally, parasympathetic fibers in CN III will be affected, causing
pupillary dilation (unopposed sympathetic innervation of the dilator of the
pupil) and an inability to accommodate the lens for close-up vision on the
affected (ipsilateral) side.
