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The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle [2] of the eye, running radially in the iris and therefore fit as a dilator. The pupillary dilator consists of a spokelike arrangement of modified contractile cells called myoepithelial cells.
Structure of the iris and surrounding parts showing the stroma of iris (stroma iridis). The stroma connects to a sphincter muscle ( sphincter pupillae ), which contracts the pupil in a circular motion, and a set of dilator muscles ( dilator pupillae ) which pull the iris radially to enlarge the pupil, pulling it in folds.
The ciliary muscle controls accommodation by altering the shape of the lens to be able to see an object from near to far. [2] The pupillary sphincter muscle and pupillary dilator muscle control the iris to adjust the size of the pupil to adjust how much light enters into the eye.
The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris.It encircles the pupil of the iris, appropriate to its function as a constrictor of the pupil.
The long ciliary nerves contain post-ganglionic sympathetic fibers from the superior cervical ganglion for the dilator pupillae muscle. [1] The sympathetic fibers to the dilator pupillae muscle mainly travel in the nasociliary nerve but there are also sympathetic fibers in the short ciliary nerves that pass through the ciliary ganglion without forming synapses.
The iris consists of two layers: the front pigmented fibrovascular layer known as a stroma and, behind the stroma, pigmented epithelial cells.. The stroma is connected to a sphincter muscle (sphincter pupillae), which contracts the pupil in a circular motion, and a set of dilator muscles (dilator pupillae), which pull the iris radially to enlarge the pupil, pulling it in folds.
These fibres are then distributed to deep structures, including the superior tarsal muscle and pupillary dilator muscle. [2] It includes fibres destined for the pupillary dilator muscle as part of a neural circuit regulating pupillary dilatation component of the pupillary reflex. [3] Some fibres of the plexus converge to form the deep petrosal ...
The muscles it controls are the striated muscle in levator palpebrae superioris and other extraocular muscles except for the superior oblique muscle and the lateral rectus muscle. The Edinger-Westphal nucleus supplies parasympathetic fibers to the eye via the ciliary ganglion , and thus controls the sphincter pupillae muscle (affecting pupil ...