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facial muscle of mouth; 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.
Etymology: L, ridere, to laugh
one of the 12 muscles of the mouth. A muscular fibrous band, it arises in the fascia over the masseter and inserts into the skin at the corner of the mouth. It acts to retract the angle of the mouth, as in a smile.
risorius(rī-sŏ′rē-ŭs) [L., laughing]
The muscular fibrous band arising over the masseter muscle and inserted into the tissues at the corner of the mouth.
n a muscle of facial expression in the orofacial re-gion that is used when smiling widely.