Risorius originates in the fascia of the masseter below the zygomatic arch and inserts in the skin near the corner of the mouth. It acts to stretch the mouth laterally, retracting the corners of the mouth, and has been thought (erroneously) to produce "grinning" or "smiling." It has a connection with the platysma in that it often contracts with it.

Risorius is innervated by the zygomatic and buccal branches of the facial nerve (VII) and is supplied with blood by the facial artery.