The ciliary ganglion (AB1) is a small, flat body lying laterally to the optical nerve in the orbit. Its parasympathetic fibers from the Edinger – Westphal nucleus run in the oculomotor nerve (AB2) and cross over to theganglion as oculomotor root (AB3) (para-sympathetic root). The preganglionic sym-pathetic fibers originate from the lateral horn of the spinal cord C8 – T2 (ciliospinalcenter) (B4) and synapse in thesuperior cer-vical ganglion (B5). The postganglionicfibers ascend in the carotid plexus (B6) as sympathetic root (B7) to the ciliary ganglion.Sensory fibers originate from the nasociliarynerve (nasociliary root) (AB8).
The short ciliary nerves (AB9) extend from the ganglion to the eyeball and penetrate the sclera to enter the interior of the eyeball. Their parasympathetic fibers innervate the ciliary muscle (accommodation) and the sphincter pupillae muscle; the sympatheticfibers innervate the dilator pupillae muscle.
Clinical Note: The pupil is antagonistically in-nervated by parasympathetic fibers (constriction of pupil) and sympathetic fibers (dilatation of pupil). Injury to the ciliospinal center or the spi-nal roots C8, T1 (paralysis of the lower brachial plexus, p. 74) results in ipsilateral constriction ofthe pupil.