Iris sphincter muscle
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| Iris sphincter | ||
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| Iris, front view. (Muscle visible but not labeled.) | ||
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| The upper half of a sagittal section through the front of the eyeball. ("Circular fibers" labeled near center.) | ||
| Latin | m. sphincter pupillae | |
| Gray's | subject #225 1013 | |
| Origin: | ||
| Insertion: | ||
| Blood: | ||
| Nerve: | short ciliary nerves | |
| Action: | constricts pupil | |
| Antagonist: | iris dilator muscle | |
| Dorlands/Elsevier | m_22/12550831 | |
The iris sphincter muscle (pupillary sphincter, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris.
It is found in vertebrates and some cephalopods.
In humans, it functions to constrict the pupil in bright light (pupillary reflex) or during accommodation.
It is controlled by parasympathetic fibers that originate from the Edinger-Westphal nucleus, travel along the oculomotor nerve (CN III), synapse in the ciliary ganglion, and then enter the eye via the short ciliary nerves
[edit] Additional images
 Sympathetic connections of the ciliary and superior cervical ganglia. |
[edit] See also
[edit] External links
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