dilator pupillae muscle
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di·la·tor pu·pil·lae mus·cle[TA]
intrinsic so-called muscle of eyeball; radially disposed layer of muscular processes of the myoepithelial cells that form the epithelium of the posterior surface of the iris, which extends from the pupillary to the ciliary margin; sympathetic stimulation causes contraction, which slowly dilates the pupil to allow more light to reach the retina.
Synonym(s): musculus dilatator pupillae [TA], dilator iridis, dilator of pupil, musculus dilator iridis
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