What is the function of sphincter pupillae?

The sphincter muscle fibers 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.

What is the function of dilator Pupillae muscle?

Function. The pupillary dilator acts to increase the size of the pupil to allow more light to enter the eye. It works in opposition to the pupillary constrictor.

What is the primary function of the iris sphincter and dilator muscles?

The iris sphincter and dilator muscles control pupil size, with parasympathetic sphincter muscle innervation originating in the Edinger–Westphal subnucleus of the third cranial nerve in the midbrain.

Is sphincter pupillae a smooth muscle?

As does cardiac muscle, much of the smooth muscle in the body arises from splanchnic mesoderm. Exceptions are the ciliary muscle and sphincter pupillae muscles of the eye, which are derived from neural crest ectoderm, and much of the vascular smooth muscle, which frequently arises from the local mesoderm.

What is the muscle that encircles the eye known?

The orbicularis oculi muscles circle the eyes and are located just under the skin. Parts of this muscle act to open and close the eyelids and are important muscles in facial expression.

Which specific system controls the dilator muscles?

Pupillary diameter, or more precisely iris size, is controlled by two muscles, the sphincter pupillae, which is primarily under the control of the parasympathetic nervous system, and the dilator pupillae, which is primarily under the control of the sympathetic nervous system.

What happens when the radial muscles of the iris contract?

In bright light, the circular muscles contract whilst the radial muscles relax. This causes the pupil to constrict and less light enters the eye. In dim conditions the opposite occurs. The circular muscles relax and the radial muscles contract, causing the pupil to dilate and allowing more light to pass into the eye.

What is the role of the ora serrata?

The ora serrata is the serrated junction between the choroid and the ciliary body. This junction marks the transition from the simple, non-photosensitive area of the ciliary body to the complex, multi-layered, photosensitive region of the retina.

What is the sphincter pupillae?

Origin and insertion Sphincter pupillae is a circular muscle, about 1 millimeter wide. It is located in the pupillary zone of stromal layer of the iris, attaching to and encircling the pupillary margin of iris.

Where is the sphincter muscle in the eye?

The sphincter muscle fibers are located near the pupillary margin and are slightly anterior to the pigmented epithelium of the iris. It encircle … The iris sphincter muscle, also known as the pupillary sphincter or sphincter pupillae, is a muscle located in the colored part of the eye called the iris.

What is the iris sphincter muscle?

The iris sphincter muscle, also known as the pupillary sphincter or sphincter pupillae, is a muscle located in the colored part of the eye called the iris. The sphincter muscle fibers are located near the pupillary margin and are slightly anterior to the pigmented epithelium of the iris.

How is the diameter of the pupil regulated?

The diameter of the pupil is dynamic and it is regulated by a pair of antagonistic muscles found in the iris; the sphincter pupillae and the dilator pupillae. Both of these muscles are smooth muscles, functioning beyond the control of our will. Their function is to change the diameter of the pupil during two reflexive events;