All Topics  
Ciliary muscle

 

 
   Email Print
   Bookmark   Link
 

 

Ciliary muscle
 
 
  Topics Ciliary muscle Topic Home

The ciliary muscle is a muscle in the eye that controls the eye's accommodation for viewing objects at varying distances.

ciliary muscle affects zonular fibers
Zonule of Zinn

The zonule of Zinn is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye. The zonule is split into two layers: a thin layer which lines the hyaloid fossa and a thicker layer which is a collection of zonular fibers....
 in the eye
Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
 (fibers that suspend the lens
Lens (anatomy)

The lens is a transparent, Lens_#Types_of_lenses structure in the eye that, along with the cornea, helps to refract light to be Focus on the retina....
 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.






Discussion
Ask a question about 'Ciliary muscle'
Start a new discussion about 'Ciliary muscle'
Answer questions from other users
Full Discussion Forum



Recent Posts

What happens to the eye when looking at objects far in the distance, the lens is __________ and the ...








Encyclopedia


The ciliary muscle is a muscle in the eye that controls the eye's accommodation for viewing objects at varying distances.

Mode of action

The ciliary muscle affects zonular fibers
Zonule of Zinn

The zonule of Zinn is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye. The zonule is split into two layers: a thin layer which lines the hyaloid fossa and a thicker layer which is a collection of zonular fibers....
 in the eye
Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
 (fibers that suspend the lens
Lens (anatomy)

The lens is a transparent, Lens_#Types_of_lenses structure in the eye that, along with the cornea, helps to refract light to be Focus on the retina....
 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.

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
Oculomotor nerve

The oculomotor nerve is the third of twelve paired cranial nerves. It controls most of the eye's movements, constriction of the pupil, and maintains an open eyelid....
) synapsing on the ciliary ganglion
Ciliary ganglion

The ciliary ganglion is a Parasympathetic nervous system ganglion located in the posterior Orbit . It measures 1?2 millimeters in diameter and contains approximately 2,500 neurons....
. 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.

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.

See also

  • Accommodation reflex
    Accommodation reflex

    The accommodation reflex is a reflex action of the eye, in response to focus on a near object, then looking at distant object , comprising coordinated changes in vergence, lens shape and pupil size....
  • Ciliary body
    Ciliary body

    The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle and ciliary processes. It is triangular in horizontal section, and is coated by a double layer, the ciliary epithelium....
  • Cycloplegia
    Cycloplegia

    Cycloplegia is paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation . ...
  • Presbyopia
    Presbyopia

    Presbyopia describes the condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Presbyopia's exact mechanisms are not known with certainty, however, the research evidence most strongly supports a loss of elasticity of the Lens , although changes in the lens's curvature from continual growth and...
  • Edinger-Westphal nucleus
    Edinger-Westphal nucleus

    The Edinger-Westphal nucleus is the accessory parasympathetic nervous system cranial nerve nucleus of the oculomotor nerve , supplying the constricting muscles of the Iris ....


Additional images


External links