The<unk>  (pupillary<unk> , 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.
Iris sphincter muscle
Iris dilator muscle
Corpus cavernosum penis
Subfornical organ
Corpora quadrigemina
Oculomotor nerve
Morcellator
Penis captivus