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The ciliary ganglion is a parasympathetic ganglion 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 ''preganglionic'' axons 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: * the sphincter pupillae constricts the pupil, a movement known as Miosis. The opposite, Mydriasis, is the dilation of the pupil. * the ciliaris contracts, releasing tension on the Zonular Fibers, making the lens more convex, also known as accommodation. Both of these muscles are ''involuntary'' – they are controlled by the autonomic nervous system. It is one of four parasympathetic ganglia of the head and neck. (The others are the submandibular ganglion, pterygopalatine ganglion, and otic ganglion). ==Anatomy== Three types of nerve fibers run through the ciliary ganglion: ''parasympathetic fibers'', ''sympathetic fibers'' and ''sensory fibers''. Only parasympathetic fibers form synapses in the ganglion. The other two types of nerve fibers simply pass through. In classical anatomy, the ciliary ganglion is said to have three “roots:” * a parasympathetic root of ciliary ganglion (or ''motor root'') * a sympathetic root of ciliary ganglion * a sensory root of ciliary ganglion 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ciliary ganglion」の詳細全文を読む スポンサード リンク
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