Walsh & Hoyt: Ocular Motor Nuclei and Nerves

The oculomotor nerve (the third nerve) is the largest and most complex of the three ocular motor nerves. It contains somatic motor fibers that innervate the superior, inferior, and medial recti, the inferior oblique, and the levator palpebrae superioris. It also contains visceral (parasympathetic) motor fibers that innervate the ciliary and the iris sphincter muscles. In addition to somatic and visceral motor fibers, the oculomotor nerve carries fibers from the trigeminal nerve and the sympathetic plexus. In humans, the oculomotor nerve has about 15,000 axons (four times the number in the abducens nerve and seven times the number in the trochlear nerve), most of which are distributed to about 40,000 muscle fibers.