Ciliary muscle
The choroid and iris. (Ciliary muscle is labeled near top.)
Latin	musculus ciliaris
Gray's	subject #225 1011
Origin:
Insertion:
Artery:	Long ciliary arteries
Nerve:	Oculomotor nerve (parasympathetics)
Action:	accommodation
Dorlands/Elsevier	m_22/12548589

The ciliary muscle is a smooth muscle of the head that is responsible for accommodation of the eye Image File history File links Gray872. ... The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye lying between the retina and the sclera. ... In anatomy, the iris (plural irises or irides) is the most visible part of the eye of vertebrates, including humans. ... For other uses, see Latin (disambiguation). ... A typical adult human skeleton consists of the following 206 bones depending on age, though this number does vary owing to a variety of anatomical variations; for example, a small portion of the human population have an extra rib, or an extra lumbar vertebra. ... A typical adult human skeleton consists of the following 206 bones depending on age, though this number does vary owing to a variety of anatomical variations; for example, a small portion of the human population have an extra rib, or an extra lumbar vertebra. ... Section of an artery For other uses, see Artery (disambiguation). ... List of human nerves External links List of nerves This is an incomplete list, which may never be able to satisfy certain standards for completeness. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... Anatomy and Physiology of the A.N.S. In contrast to the voluntary nervous system, the involuntary or autonomic nervous system is responsible for homeostasis, maintaining a relatively constant internal environment by controlling such involuntary functions as digestion, respiration, and metabolism, and by modulating blood pressure. ... Look up kinesiology in Wiktionary, the free dictionary. ... Human eye The Accommodation Reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa). ... Elseviers logo. ... Smooth muscle Layers of Esophageal Wall: 1. ...

Mode of action

The ciliary muscle affects 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 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. The zonule of Zinn is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye. ... For other uses, see Eye (disambiguation). ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ...

The other way around, relaxation of the ciliary muscle causes the zonular fibers to become taut, flattening the lens, increasing long range focus.

Innervation

Contraction of the lens happens when there is parasympathetic activation of the M3 muscarinic receptors on the ciliary muscles. The parasympathetic signal is carried by cranial nerve III (the oculomotor nerve) synapsing on the ciliary ganglion. This leads to contraction of the ciliary muscles, a consequent reduction in the size of the ciliary body, and a lessening of the tension on the lens, hence allowing the lens to spring back into a more spherical shape to accommodate for close vision. Anatomy and Physiology of the A.N.S. In contrast to the voluntary nervous system, the involuntary or autonomic nervous system is responsible for homeostasis, maintaining a relatively constant internal environment by controlling such involuntary functions as digestion, respiration, and metabolism, and by modulating blood pressure. ... Amanita muscaria from which muscarine was isolated Acetylcholine - natural agonist of muscarinic and nicotinic receptors. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... The ciliary ganglion is small parasympathetic ganglion lying in the orbit between the optic nerve and the lateral rectus muscle that is associated with the nasociliary nerve (a branch of the ophthalmic division of the trigeminal nerve). ...

Unlike the muscles of the iris (which receives both types of autonomic innervation--the iris sphincter is exclusively innervated by parasympathetics and the iris dilator exclusively by sympathetics), the ciliary muscle receives only parasympathetic innervation. The iris sphincter muscle (pupillary sphincter, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. ... The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a muscle of the eye. ...

See also

• accommodation reflex
• Ciliary body
• Cycloplegia
• Presbyopia
• Edinger-Westphal nucleus

Human eye The Accommodation Reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa). ... Schematic diagram of the human eye The ciliary body is the part of the eye containing the ciliary muscle and ciliary processes. ... Cycloplegia is the paralysis of the ciliary muscle, resulting in a loss of accommodation. ... Presbyopia (Greek word presbyteros (πρεσβύτερος), meaning elder) is the eyes diminished ability to focus that occurs with aging. ... The Edinger-Westphal nucleus is the accessory parasympathetic nucleus of the oculomotor nerve, supplying the constricting muscles of the iris. ...

Additional images

Sympathetic connections of the ciliary and superior cervical ganglia. From Grays Anatomy This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ...

The arteries of the choroid and iris. The greater part of the sclera has been removed. Image File history File links No higher resolution available. ...

Iris, front view. Image File history File links Gray878. ...

External links

• Ciliary+muscle at eMedicine Dictionary