A sphincter muscle that is part of the iris. [ http://en.wikipedia.org/wiki/Iris_sphincter_muscle ]

Synonyms: iris sphincter muscle musculus sphincter pupillae M. sphincter pupillae sphincter muscle of pupil

This is just here as a test because I lose it

Term information



depicted by


function notes

constricts iris

has related synonym

sphincter pupillae

pupillary constrictor muscle

pupillary sphincter

constrictor pupillae

sphincter pupillae muscle

m. sphincter pupillae

pupillary sphincter muscle

circular fibers

spincter pupillae

iris constrictor

iris sphincter

iris constrictor muscle



taxon notes

WP says: It is found in vertebrates and some cephalopods; this class refers to the vertebrate structure

In humans, it functions to constrict the pupil in bright light or during accommodation. Its dimensions are about 0.75 mm wide by 0.15 mm thick. It is controlled by parasympathetic fibers that originate from the Edinger-Westphal nucleus, travel along the oculomotor nerve (CN III), synapse in the ciliary ganglion, and then enter the eye via the short ciliary nerves. Initially, all the myocytes are of the smooth muscle type, but much later in life, so that ultimately most cells are of the striated muscle type. [WP,unvetted]