Ciliary muscle

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
Actions	1) accommodation, 2) regulation of trabecular meshwork pore sizes
Identifiers
Latin	musculus ciliaris
Dorlands /Elsevier	ciliary muscle
TA	A15.2.03.014
FMA	49151
Anatomical terms of muscle []

The ciliary muscle /ˈsɪli.ɛəri/ 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.

The ciliary muscle develops from mesenchyme within the choroid and is considered a cranial neural crest derivative.

The ciliary muscle receives only parasympathetic fibers from the short ciliary nerves that arise from the ciliary ganglion. These postganglionic fibers are part of cranial nerve V (Nasociliary nerve of the trigeminal).

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. 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. The zonule fibers relax and the lens becomes more spherical, increasing its power to refract light for near vision.