(Science: anatomy, muscle) origin, from platysma and fascia of masseter; insertion, orbicularis oris and skin at corner of mouth; action, draws angle of mouth laterally, lenghthening rima oris; nerve supply, facial.
Synonym: musculus risorius, albinus’ muscle, santorini’s muscle.
Origin: L. Risor, a laughter, fr. Rideo, pp. Risus, to laugh