Iris sphincter muscle
Iris Sphincter Muscle
The Iris Sphincter Muscle (pronunciation: /ˈaɪrɪs ˈsfɪŋktər ˈmʌsl̩/), also known as the Sphincter Pupillae, is a muscle in the part of the eye called the iris. Its primary function is to control the size of the pupil, the opening that allows light to enter the eye.
Etymology
The term "Iris Sphincter Muscle" is derived from the Latin word "Iris", which means rainbow, and the Greek word "Sphincter", which means band or girdle. The term "Muscle" comes from the Latin word "Musculus", which means little mouse, a term used by the Romans to describe the appearance and movement of muscles under the skin.
Function
The Iris Sphincter Muscle contracts to constrict the pupil in response to bright light (a process known as miosis), and relaxes to dilate the pupil in response to low light (a process known as mydriasis). This action helps to regulate the amount of light that reaches the retina, the light-sensitive tissue at the back of the eye.
Related Terms
- Iris: The colored part of the eye that contains the Iris Sphincter Muscle.
- Pupil: The opening in the center of the iris that allows light to enter the eye.
- Miosis: The constriction of the pupil, which occurs in response to bright light.
- Mydriasis: The dilation of the pupil, which occurs in response to low light.
- Retina: The light-sensitive tissue at the back of the eye.
External links
- Medical encyclopedia article on Iris sphincter muscle
- Wikipedia's article - Iris sphincter muscle
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