[TA] a ring of smooth muscle fibers surrounding the pupillary border of the iris. Synonym(s): musculus sphincter pupillae [TA], sphincter muscle of pupil
sphinc·ter pu·pil·lae
(sfingk'tĕr pyū-pil'ē) [TA] A ring of smooth muscle fibers surrounding the pupillary border of the iris. Synonym(s): musculus sphincter pupillae [TA] , sphincter muscle of pupil.