The ciliary ganglion is a parasympatheticganglion located just behind the eye in the posterior orbit. It measures 1–2 millimeters in diameter and in humans contains approximately 2,500 neurons. The oculomotor nerve coming into the ganglion contains preganglionicaxons from the Edinger-Westphal nucleus (a part of the brainstem) which form synapses with the ciliary neurons. The postganglionic axons run in the short ciliary nerves and innervate two eye muscles: