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The iris does have muscle. In fact, there are two muscles of the iris, and they both consist of smooth muscle. The iris sphincter muscle, also known as the pupillary sphincter, is a muscle located in the coloured part of the eye called the iris. It encircles the pupil of the iris and functions to constrict the pupil in bright light via the pupillary light reflex. In reptiles, the iris is made of striated muscle, while in fish, it is made of neither, meaning their pupils are always the same size.
| Characteristics | Values |
|---|---|
| Type of muscle | Smooth muscle in mammals and amphibians, striated muscle in reptiles (including birds) |
| Function | Constricts the pupil in bright light or during accommodation |
| Location | In the coloured part of the eye |
| Dimensions | 0.75 mm wide by 0.15 mm thick |
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What You'll Learn
- The iris sphincter muscle is a muscle in the iris
- The iris sphincter muscle encircles the pupil of the iris
- The iris sphincter muscle controls the pupil's diameter
- The iris sphincter muscle is found in vertebrates and some cephalopods
- The muscle cells of the iris are smooth muscle in mammals and amphibians
The iris sphincter muscle is a muscle in the iris
The iris sphincter muscle, also known as the pupillary sphincter or sphincter pupillae, is a muscle located in the coloured part of the eye called the iris. The iris sphincter muscle fibres are located near the pupillary margin and are slightly anterior to the pigmented epithelium of the iris. The muscle encircles the pupil of the iris and functions to constrict the pupil in bright light via the pupillary light reflex or during accommodation. By controlling the pupil's diameter, the iris controls the amount of light that reaches the back of the eye at the retina. The iris is a circular, pigmented diaphragm that lies anterior to the lens in a coronal plane.
The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds). Many fish have neither, and, as a result, their irises are unable to dilate and contract, so that the pupil always remains of a fixed size. The iris sphincter muscle is one of two muscles of the iris, and both consist of smooth muscle. The ciliary muscle, pupillary sphincter muscle and pupillary dilator muscle are sometimes called intrinsic ocular muscles or intraocular muscles.
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The iris sphincter muscle encircles the pupil of the iris
The iris is the coloured part of the eye and it does indeed have muscle. The iris sphincter muscle, also known as the pupillary sphincter or sphincter pupillae, encircles the pupil of the iris. It is located near the pupillary margin and is slightly anterior to the pigmented epithelium of the iris.
The iris sphincter muscle is a constrictor of the pupil. It controls the pupil's diameter, which in turn controls the amount of light that reaches the back of the eye at the retina. In bright light, the iris sphincter muscle constricts the pupil via the pupillary light reflex. This function is also referred to as 'accommodation'.
The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds). Many fish have neither, and, as a result, their irises are unable to dilate and contract, so that the pupil always remains of a fixed size.
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The iris sphincter muscle controls the pupil's diameter
The iris is the coloured part of the eye and it does contain muscle. The iris sphincter muscle, also known as the pupillary sphincter or sphincter pupillae, encircles the pupil of the iris. By controlling the pupil's diameter, the iris controls the amount of light that reaches the retina at the back of the eye. This is called the pupillary light reflex.
The iris sphincter muscle is found in vertebrates and some cephalopods. In humans, it functions to constrict the pupil in bright light or during accommodation. The muscle fibres are located near the pupillary margin and are slightly anterior to the pigmented epithelium of the iris.
The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds). Many fish have neither, and, as a result, their irises are unable to dilate and contract, so that the pupil always remains of a fixed size.
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The iris sphincter muscle is found in vertebrates and some cephalopods
The iris sphincter muscle, also known as the pupillary sphincter or sphincter pupillae, is a muscle located in the coloured part of the eye called the iris. The iris sphincter muscle is found in vertebrates and some cephalopods. The muscle fibres are located near the pupillary margin and are slightly anterior to the pigmented epithelium of the iris. It encircles the pupil of the iris and functions to constrict the pupil in bright light via the pupillary light reflex or during accommodation. By controlling the pupil's diameter, the iris controls the amount of light that reaches the back of the eye at the retina. The iris is a circular, pigmented diaphragm that lies anterior to the lens in a coronal plane.
The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds). Many fish have neither, and, as a result, their irises are unable to dilate and contract, so that the pupil always remains of a fixed size. The iris sphincter muscle is one of two muscles of the iris, and both consist of smooth muscle. The ciliary muscle, pupillary sphincter muscle and pupillary dilator muscle are sometimes called intrinsic ocular muscles or intraocular muscles.
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The muscle cells of the iris are smooth muscle in mammals and amphibians
The iris is the coloured part of the eye and contains muscle cells. In mammals and amphibians, these muscle cells are smooth muscle. Reptiles, including birds, have striated muscle cells in the iris.
The iris sphincter muscle, also known as the pupillary sphincter or sphincter pupillae, is a muscle located in the iris. It encircles the pupil and functions to constrict the pupil in bright light via the pupillary light reflex. By controlling the pupil's diameter, the iris controls the amount of light that reaches the back of the eye at the retina. The iris is a circular, pigmented diaphragm that lies anterior to the lens in a coronal plane.
The ciliary muscle, pupillary sphincter muscle and pupillary dilator muscle are sometimes called intrinsic ocular muscles or intraocular muscles. All the myocytes are of the smooth muscle type. Its dimensions are about 0.75 mm wide by 0.15 mm thick.
The sympathetic and parasympathetic systems work in opposition to constantly adjust the pupillary aperture.
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Frequently asked questions
Yes, the iris has muscle.
The iris has smooth muscle. In reptiles and birds, the iris has striated muscle.
The iris muscle controls the amount of light that reaches the back of the eye at the retina. It does this by constricting the pupil in bright light via the pupillary light reflex.
The iris muscle is called the iris sphincter muscle, or the pupillary sphincter.
