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- origin: fascia overlying the parotid, masseter and/or platysma muscles
- insertion: modiolus at the angle of the mouth
- innervation: facial nerve (VII)
- action: pulls back the angle of the mouth
The risorius muscle arises from the superficial fascia as a bundle of muscle fibers which pass anteriorly to insert into the angle of the mouth. The bundle is widest at its origin, narrowing towards its insertion.
- modiolus at the angle of the mouth 4
- buccal branch of the facial nerve (VII) 1
- pulls back the angle of the mouth 2
The risorius muscle is commonly absent. Occasionally the risorius muscle is duplicated or markedly larger than normal. The fibers of risorius may be merged into the platysma muscle 2 or fused with the transversus nuchae muscle 5.
History and etymology
Giovanni Domenico Santorini (1681-1737), described the risorius muscle, hence its historical name, muscle of Santorini 6. The German born, naturalised Dutch, anatomist Bernhard Siegfried Albinus (1697-1770), wrote a detailed treatise on the risorius muscle, such that it was also called the muscle of Albinus in the past 7.