World Library  
Flag as Inappropriate
Email this Article

Sympathetic root of ciliary ganglion

Article Id: WHEBN0016174155
Reproduction Date:

Title: Sympathetic root of ciliary ganglion  
Author: World Heritage Encyclopedia
Language: English
Subject: Ciliary ganglion, Iris dilator muscle, Sensory root of ciliary ganglion
Publisher: World Heritage Encyclopedia

Sympathetic root of ciliary ganglion

Nerve: Sympathetic root of ciliary ganglion
Pathways in the Ciliary Ganglion. Green = parasympathetic; Red = sympathetic; Blue = sensory
Latin ramus sympathetica ganglii ciliaris

The sympathetic root of ciliary ganglion is one of three roots of the ciliary ganglion, a tissue mass behind the eye. It contains postganglionic sympathetic fibers whose cell bodies are located in the superior cervical ganglion. Their axons ascend with the internal carotid artery as a plexus of nerves, the carotid plexus. Sympathetic fibers innervating the eye separate from the carotid plexus within the cavernous sinus. They run forward through the superior orbital fissure and merge with the long ciliary nerves (branches of the nasociliary nerve) and the short ciliary nerves (from the ciliary ganglion). Sympathetic fibers in the short ciliary nerves pass through the ciliary ganglion without forming synapses.

Preganglionic sympathetic fibers originate from neurons in the intermediolateral column of the thoracic spinal cord, at the level of thoracic spinal nerve 1 (T1) and thoracic spinal nerve 2 (T2). They form synapses in the superior cervical ganglion. The ratio of incoming to outgoing fibers (the “convergence”) in this ganglion is approximately 100:1. Sympathetic motor neurons in the spinal cord are controlled by supranuclear pathways that descend through the brainstem and spinal cord. Interruption of the sympathetic chain at any level (from the brainstem to the ciliary ganglion) will produce pupillary constriction (miosis) and eyelid droop (ptosis) – the classic signs of Horner's syndrome.

Sympathetic fibers from the superior cervical ganglion innervate blood vessels (vasoconstriction), sweat glands, and four eye muscles: the dilator pupillae, the superior tarsal muscle, the inferior tarsal muscle and the orbitalis.

The dilator pupillae dilates the pupil; its action is antagonistic to the sphincter pupillae. Pupil size is therefore under the dual control of sympathetic and parasympathetic nerves.

The superior tarsal muscle elevates the upper eyelid. The levator palpebrae superioris, which is innervated by a branch of the oculomotor nerve, also elevates the upper eyelid. Eyelid elevation is therefore under both voluntary and involuntary control. Interruption of either pathway will result in eyelid droop (ptosis).

The other two eye muscles with sympathetic innervation (the inferior tarsal muscle and the orbitalis) are vestigial in humans. They are variable and often incompletely developed.

See also

External links


This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.