Ciliary muscle - wikipedia Ciliary muscle This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( December 2016 ) Ciliary muscle The choroid and iris. ( Ciliary muscle is labeled near top. ) Details Origin 1 ) longitudinal fibers → scleral spur ; 2 ) circular fibers → encircle root of iris Insertion 1 ) longitudinal fibers → ciliary process, 2 ) circular fibers → encircle root of iris Artery long posterior ciliary arteries Vein Vorticose vein Nerve short ciliary From oculomotor nerve Through ciliary ganglion Sympathetic postganglionic fibers from sup. cervical ganglia. Actions 1 ) accommodation, 2 ) regulation of trabecular meshwork pore sizes Identifiers Latin musculus ciliaris TA A15. 2.03. 014 FMA 49151 Anatomical terms of muscle ( edit on Wikidata ) The ciliary muscle / ˈsɪli. ɛər i / is a ring of smooth muscle in the eye 's middle layer ( vascular layer ) that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm 's canal. It changes the shape of the lens within the eye, not the size of the pupil which is carried out by the sphincter pupillae muscle and dilator pupillae. Contents 1 Structure 1.1 Development 1.2 Innervation 2 Function 2.1 Accommodation 2.2 Trabecular meshwork pore size 3 Clinical significance 3.1 Glaucoma 4 History 4.1 Etymology 5 Additional images 6 See also 7 References 8 Bibliography 9 External links Structure Development The ciliary muscle develops from mesenchyme within the choroid and is considered a cranial neural crest derivative. Innervation Ciliary ganglion with parasympathetic fibers of ciliary nerves. The ciliary muscle receives parasympathetic fibers from the short ciliary nerves that arise from the ciliary ganglion. The sympathetic postganglionic fibers are part of cranial nerve V ( Nasociliary nerve of the trigeminal ). The postganglionic sympathetic innervation arises from the superior cervical ganglia Presynaptic parasympathetic signals that originate in the Edinger - Westphal nucleus are carried by cranial nerve III ( the oculomotor nerve ) and travel through the ciliary ganglion via the postganglionic parasympathetics fibers which travel in the short ciliary nerves and supply the ciliary body and iris. Parasympathetic activation of the M3 muscarinic receptors causes ciliary muscle contraction, the effect of contraction is to decrease the diameter of the ring of ciliary muscle ( causing constriction of the pupil and accommodation ). The zonule fibers relax and the lens becomes more spherical, increasing its power to refract light for near vision. The parasympathetic tone is dominant when a higher degree of accommodation of the lens is required, such as reading a book. Function Accommodation Main article : accommodation of the eye The ciliary fibers have circular ( Ivanoff ), longitudinal ( meridional ) and radial orientations. According to Hermann von Helmholtz 's theory, the circular ciliary muscle fibers affect zonular fibers in the eye ( fibers that suspend the lens in position during accommodation ), enabling changes in lens shape for light focusing. When the ciliary muscle contracts, it pulls itself forward and moves the frontal region toward the axis of the eye. This releases the tension on the lens caused by the zonular fibers ( fibers that hold or flatten the lens ). This release of tension of the zonular fibers causes the lens to become more spherical, adapting to short range focus. Conversely, relaxation of the ciliary muscle causes the zonular fibers to become taut, flattening the lens, increasing the focal distance, increasing long range focus. Although Helmholtz 's theory has been widely accepted since 1855, its mechanism still remains controversial. Alternative theories of accommodation have been proposed by others, including L. Johnson, M. Tscherning, and especially Ronald A. Schachar. Trabecular meshwork pore size Contraction and relaxation of the longitudinal fibers, which insert into the trabecular meshwork in the anterior chamber of the eye, cause an increase and decrease in the meshwork pore size, respectively, facilitating and impeding aqueous humour flow into the canal of Schlemm. Clinical significance Glaucoma Open - angle glaucoma ( OAG ) and closed - angle glaucoma ( CAG ) may be treated by muscarinic receptor agonists ( e.g., pilocarpine ), which cause rapid miosis and contraction of the ciliary muscles, opening the trabecular meshwork, facilitating drainage of the aqueous humour into the canal of Schlemm and ultimately decreasing intraocular pressure. History Etymology The word ciliary had its origins around 1685 -- 1695. The term cilia originated a few years later in 1705 -- 1715, and is the Neo-Latin plural of cilium meaning eyelash. In Latin, cilia means upper eyelid and is perhaps a back formation from supercilium, meaning eyebrow. The suffix - ary originally occurred in loanwords from Middle English ( - arie ), Old French ( - er, - eer, - ier, - aire, - er ), and Latin ( - ārius ) ; it can generally mean `` pertaining to, connected with '', `` contributing to '', and `` for the purpose of ''. Taken together, cili ( a ) - ary pertains to various anatomical structures in and around the eye, namely the ciliary body and annular suspension of the lens of the eye. Additional images The arteries of the choroid and iris. The greater part of the sclera has been removed. Iris, front view. See also This article uses anatomical terminology ; for an overview, see Anatomical terminology. Accommodation reflex Ciliary body Cycloplegia Presbyopia References ^ Jump up to : Gest, Thomas R ; Burkel, William E. `` Anatomy Tables - Eye. '' Medical Gross Anatomy. 2000. University of Michigan Medical School. January 5, 2010 Umich.edu Archived 2010 - 05 - 26 at the Wayback Machine. ^ Jump up to : Kleinmann, G ; Kim, H.J. ; Yee, R.W. ( 2006 ). `` Scleral expansion procedure for the correction of presbyopia ''. International ophthalmology clinics. 46 ( 3 ) : 1 -- 12. PMID 16929221. Jump up ^ Schachar, Ronald A. ( 2012 ). `` Anatomy and Physiology. '' ( Chapter 4 ) The Mechanism of Accommodation and Presbyopia. Kugler Publications. ISBN 978 - 9 - 062 - 99233 - 1. Jump up ^ Dudek RW, Fix JD ( 2004 ). `` Eye '' ( chapter 9 ). Embryology - Board Review Series ( 3rd edition, illustrated ). Lippincott Williams & Wilkins. p. 92. ISBN 0 - 7817 - 5726 - 6, ISBN 978 - 0 - 7817 - 5726 - 3. Books.Google.com. Retrieved on 2010 - 01 - 17 from https://books.google.com/books?id=MmoJQWsJteoC. Jump up ^ Moore KL, Dalley AF ( 2006 ). `` Head ( chapter 7 ) ''. Clinically Oriented Anatomy ( 5th ed. ). Lippincott Williams & Wilkins. p. 972. ISBN 0 - 7817 - 3639 - 0. Jump up ^ McDougal, David H. ; Gamlin, Paul D. ( January 2015 ). `` Autonomic control of the eye ''. Comprehensive Physiology. 5 ( 1 ) : 439 -- 473. doi : 10.1002 / cphy. c140014. ISSN 2040 - 4603. PMC 4919817. PMID 25589275. Jump up ^ Brunton, L.L. ; Chabner, Bruce ; Knollmann, Björn C., eds. ( 2011 ). Goodman & Gilman 's The Pharmacological Basis of Therapeutics ( 12 ed. ). New York : McGraw - Hill. ISBN 978 - 0 - 07 - 162442 - 8. Jump up ^ `` Ocular Embryology with Special Reference to Chamber Angle Development ''. The Glaucomas. 2009. pp. 61 -- 9. doi : 10.1007 / 978 - 3 - 540 - 69146 - 4_8. ISBN 978 - 3 - 540 - 69144 - 0. Jump up ^ Riordan - Eva Paul, `` Chapter 1. Anatomy & Embryology of the Eye '' ( Chapter ). Riordan - Eva P, Whitcher JP ( 2008 ). Vaughan & Asbury 's General Ophthalmology ( 17th ed. ). McGraw - Hill. AccessMedicine.com Archived 2009 - 07 - 06 at the Wayback Machine. Jump up ^ Brunton, Laurence L. ; Lazo, John S. ; Parker, Keith, eds. ( 2005 ). Goodman & Gilman 's The Pharmacological Basis of Therapeutics ( 11th ed. ). New York : McGraw - Hill. pp. 134 -- 135. ISBN 978 - 0 - 07 - 162442 - 8. Jump up ^ Salmon John F, `` Chapter 11. Glaucoma '' ( Chapter ). Riordan - Eva P, Whitcher JP ( 2008 ). Vaughan & Asbury 's General Ophthalmology ( 17th ed. ). McGraw - Hill. AccessMedicine.com Archived 2009 - 07 - 06 at the Wayback Machine. Jump up ^ Le, Tao T. ; Cai, Xumei ; Waples - Trefil, Flora. `` QID : 22067 ''. USMLERx. MedIQ Learning, LLC. 2006 -- 2010. 13 January 2010 Usmlerx.com Jump up ^ `` cilia '', Unabridged. Source location : Random House, Inc. Reference.com. Retrieved on 2010 - 01 - 16 from http://dictionary.reference.com/browse/cilia. Jump up ^ Dictionary.com, `` - ary '', in The American Heritage Dictionary of the English Language, Fourth Edition. Source location : Houghton Mifflin Company, 2004. Reference.com. Retrieved on 2010 - 01 - 16 from http://dictionary.reference.com/browse/-ary. Jump up ^ `` ciliary, '' in Dictionary.com Unabridged. Source location : Random House, Inc. Reference.com. Retrieved on 2010 - 01 - 16 from http://dictionary.reference.com/browse/ciliary. Bibliography This section is empty. You can help by adding to it. ( February 2017 ) External links Lens, zonule fibers, and ciliary muscles -- SEM Anatomy of the globe of the eye Fibrous tunic ( outer ) Sclera Episcleral layer Schlemm 's canal Trabecular meshwork Cornea Limbus layers Epithelium Bowman 's Stroma Dua 's layer Descemet 's Endothelium Uvea / vascular tunic ( middle ) Choroid Capillary lamina of choroid Bruch 's membrane Sattler 's layer Ciliary body Ciliary processes Ciliary muscle Pars plicata Pars plana Iris Stroma Pupil Iris dilator muscle Iris sphincter muscle Retina ( inner ) Layers Inner limiting membrane Nerve fiber layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting membrane Layer of rods and cones Retinal pigment epithelium Cells Photoreceptor cells ( Cone cell, Rod cell ) → ( Horizontal cell ) → Bipolar cell → ( Amacrine cell ) → Retina ganglion cell ( Midget cell, Parasol cell, Bistratified cell, Giant retina ganglion cells, Photosensitive ganglion cell ) → Diencephalon : P cell, M cell, K cell, Muller glia Other Macula Perifoveal area Parafoveal area Fovea Foveal avascular zone Foveola Optic disc Optic cup Ora serrata Anatomical regions of the eye Anterior segment Adnexa Fibrous tunic Anterior chamber Aqueous humour Iris Posterior chamber Ciliary body Lens Capsule of lens Zonule of Zinn Posterior segment Vitreous chamber Vitreous body Retina Choroid Other Keratocytes Ocular immune system Tapetum lucidum Eye care professional Eye disease Refractive error Accommodation Physiological Optics Visual perception Optical illusions List of optical illusions Afterimage Barberpole Bezold Blivet Café wall Cornsweet Delboeuf Ebbinghaus Ehrenstein Flash lag Fraser spiral Grid Hering Jastrow Mach McCollough Müller - Lyer Necker Orbison Penrose stairs triangle Peripheral drift Poggendorff Ponzo Rubin Sander Schroeder Ternus Vertical -- horizontal White 's Wundt Zöllner Related Auditory Tactile Temporal Op art Ascending and Descending Waterfall Retrieved from `` https://en.wikipedia.org/w/index.php?title=Ciliary_muscle&oldid=825173489 '' Categories : Muscles of the head and neck Human eye anatomy Hidden categories : Pages with unresolved properties Webarchive template wayback links Articles needing additional references from December 2016 All articles needing additional references All articles with unsourced statements Articles with unsourced statements from January 2017 Articles with unsourced statements from December 2016 Articles to be expanded from February 2017 All articles to be expanded Articles with empty sections from February 2017 All articles with empty sections Articles using small message boxes Talk Contents About Wikipedia Català Čeština Español Euskara فارسی Galego Hrvatski Bahasa Indonesia Italiano Magyar Nederlands 日本 語 Polski Português Русский Slovenčina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska ไทย Українська Edit links This page was last edited on 11 February 2018, at 22 : 24. 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Question: what is the function of the ciliary muscle
Answer: controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm's canal