Sphincter pupillae muscle

Sphincter Pupillae Muscle

File:Sphincter pupillae.png

Sphincter pupillae muscle (Image courtesy of Gray's Anatomy)

The Sphincter pupillae muscle is a muscle in the human eye that controls the size of the pupil. It is a circular muscle that forms a ring around the pupil, and is responsible for constricting the pupil in response to bright light.

Structure

The sphincter pupillae muscle is located in the iris of the eye. It is a smooth muscle that forms a ring around the pupil. The muscle fibers are arranged in a circular pattern, allowing the muscle to constrict the pupil when it contracts.

Function

The primary function of the sphincter pupillae muscle is to control the size of the pupil. It does this by constricting the pupil in response to bright light, a process known as miosis. This helps to protect the retina from damage caused by excessive light exposure.

Clinical significance

Damage to the sphincter pupillae muscle can result in a condition known as mydriasis, which is characterized by an abnormally dilated pupil. This can occur as a result of injury, disease, or the use of certain drugs.

See also

• Dilator pupillae muscle
• Pupil
• Iris (anatomy)

References

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External links

• Wikimedia Commons has media related to Sphincter pupillae muscle.
• Wikimedia Commons has media related to Human eye anatomy.