What nerve Innervates the dilator pupillae?
sympathetic nervous system
The dilator pupillae muscle is innervated by the sympathetic nervous system. Postganglionic sympathetic fibers project from the superior cervical ganglion to join the carotid plexus. These fibers then course with the ophthalmic artery, forming a number of long ciliary nerves that supply the dilator pupillae muscle 2.
What is the function of the sphincter pupillae and dilator pupillae?
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….Sphincter pupillae.
| Origin and insertion | Pupillary margin of iris |
|---|---|
| Blood supply | Long posterior ciliary arteries, anterior ciliary arteries (via minor arterial circle) |
How does the dilator pupillae work?
dilator muscle, any of the muscles that widen a body part. In humans, the dilator muscle of the iris contains fibres that extend radially through the iris of the eye and involuntarily contract as available light decreases, thus dilating the pupil.
What happens when dilator pupillae contracts?
The pupillary dilator consists of a spokelike arrangement of modified contractile cells called myoepithelial cells. These cells are stimulated by the sympathetic nervous system. When stimulated, the cells contract, widening the pupil and allowing more light to enter the eye.
What supplies the dilator pupillae?
The dilator pupillae muscle is innervated by non-myelinated sympathetic fibres whose cell bodies are situated in the superior cervical sympathetic ganglion.
Which division of ANS stimulates the dilator pupillae muscle to dilate the pupil?
The basic autonomic mechanism controlling the pupil is straightforward: pupil constriction is mediated via parasympathetic activation of the circular sphincter pupillae muscle, and dilation via sympathetic activation of the radial dilator pupillae muscle (1).
What is sphincter pupillae?
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 the process of mydriasis takes place?
Mydriasis occurs with a rise in intraocular pressure due to the dilated iris blocking drainage of the intraocular fluid from the angle of the anterior chamber. An attack of glaucoma may be induced in eyes predisposed to primary angle (also called acute closed-angle or narrow-angle) closure and is a medical emergency.
What muscle dilates and constricts the pupil?
… in pupil size are caused by two antagonistic muscles (Fig. 1b): the dilator pupillae, which is located in the outer parts of the iris and dilates the pupil, and the sphincter pupillae, located in the central parts and constricting it.
What is the function of sphincter pupillae muscle in which conditions its works?
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.