Ciliary ganglion
Ciliary Ganglion
The Ciliary Ganglion (pronunciation: sil-ee-air-ee gang-lee-on) is a parasympathetic ganglion located in the posterior orbit. It is one of the four parasympathetic ganglia of the head and neck. Its branches, the short ciliary nerves, innervate the muscles controlling the lens and the constrictor of the pupil.
Etymology
The term "Ciliary Ganglion" is derived from the Latin word "cilium" which means eyelash and the Greek word "ganglion" which means a swelling or knot.
Structure
The Ciliary Ganglion is a small, roughly cylindrical structure approximately 2 mm long and 1.5 mm in diameter. It is located in the posterior part of the orbit, between the lateral rectus muscle and the optic nerve. It receives a sensory root from the nasociliary nerve, a motor root from the inferior division of the oculomotor nerve, and sympathetic root from the Cavernous Plexus.
Function
The Ciliary Ganglion serves as a relay station for parasympathetic fibers traveling to the eye. It provides parasympathetic innervation to the Sphincter Pupillae muscle, which constricts the pupil, and the Ciliary Muscle, which controls the shape of the lens.
Related Terms
- Parasympathetic Nervous System: The part of the autonomic nervous system that slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles.
- Oculomotor Nerve: The third cranial nerve, which controls most of the eye's movements and pupil constriction.
- Cavernous Plexus: A network of veins located in the middle cranial fossa.
- Sphincter Pupillae: The muscle in the human eye that constricts the pupil in bright light.
- Ciliary Muscle: A ring of smooth muscle in the eye's middle layer that controls accommodation for viewing objects at varying distances.
External links
- Medical encyclopedia article on Ciliary ganglion
- Wikipedia's article - Ciliary ganglion
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