dilator pupillae (dilator iridis)

Introduction

Intrinsic muscle of the eyeball, consisting of a radially disposed layer of musclar processes of myoepithelial cells that form the epithelium of the posterior surface of the iris, extending from the pupillary to the ciliary margin.

Action

• sympathetic stimulation causes contraction, which slowly dilates the pupil to allow more light to reach the retina

More general terms

• smooth muscle (unstriated/unstriped/visceral muscle)