Iris dilator muscle

Iris Dilator Muscle

File:Iris dilator muscle.jpg

Illustration of the iris dilator muscle

The Iris Dilator Muscle (also known as the pupil dilator muscle or radial muscle of the iris) is a smooth muscle of the eye, running radially in the iris and therefore fit as a dilator. The muscle fibers are arranged radially around the pupil forming a series of thin, flat bundles that lie superficially on the anterior surface of the iris.

Structure

The iris dilator muscle is a thin layer of radially oriented myocytes located just anterior to the iris pigment epithelium. It is responsible for dilating the pupil in response to sympathetic stimulation. The muscle fibers are arranged radially around the pupil, forming a series of thin, flat bundles that lie superficially on the anterior surface of the iris.

Function

The primary function of the iris dilator muscle is to control the size of the pupil. It dilates the pupil in response to low light conditions, allowing more light to reach the retina. This is a sympathetic response, meaning it is involuntary and controlled by the autonomic nervous system.

Clinical Significance

Abnormalities or damage to the iris dilator muscle can result in a number of eye conditions, including anisocoria (unequal pupil size), mydriasis (excessive dilation of the pupil), and Horner's syndrome (a condition characterized by miosis, or constriction of the pupil, among other symptoms).

See Also

• Iris (eye)
• Pupil
• Sphincter pupillae muscle
• Sympathetic nervous system