Ciliary muscle

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Ciliary muscle
The choroid and iris. (Ciliary muscle is labeled near top.)
Latin	musculus ciliaris
Gray's	subject #225 1011
Nerve	oculomotor nerve (parasympathetics)
Dorlands/Elsevier	m_22/12548589

The ciliary muscle is a smooth muscle that 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). The release of tension of the zonular fibers causes the lens to become more spherical. Therefore, relaxation of the ciliary muscle causes the zonular fibers to become taught, flattening the lens, increasing long range focus.

Contents 1 Innervation 2 See also 3 Additional images 4 External links

[edit] Innervation

Contraction of the lens happens when there is parasympathetic activation of the M3 muscarinic receptors on the ciliary muscles (contraction of the ciliary muscles reduces the size of the ciliary body, lessening the tension on the lens and allowing it to assume a more sperical shape for close vision).

Unlike the muscles of the iris (which receives both types of autonomic innervation), the ciliary muscle receives only parasympathetic innervation.

[edit] See also

• Ciliary body
• Cycloplegia
• Presbyopia

[edit] Additional images

Sympathetic connections of the ciliary and superior cervical ganglia.

The arteries of the choroid and iris. The greater part of the sclera has been removed.

Iris, front view.

[edit] External links

• Dictionary at eMedicine Ciliary+muscle