Risorius

Muscle infobox
Name = Risorius
Latin = musculus risorius
GraySubject = 108
GrayPage = 385

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Caption = Muscles of the head, face, and neck.
Origin = parotid fascia
Insertion = modiolus
Blood = facial artery
Nerve = Buccal branch of the facial nerve
Action = draw back angle of mouth
DorlandsPre = m_22
DorlandsSuf = 12550552
The risorius arises in the fascia over the parotid gland and, passing horizontally forward, superficial to the platysma, inserts onto the skin at the angle of the mouth. It is a narrow bundle of fibers, broadest at its origin, but varies much in its size and form.

Action

The risorius retracts the angle of the mouth to produce a smile, albeit an insincere-looking one that does not involve the skin around the eyes. Compare with a real smile, which raises the lips with the action of zygomaticus major and zygomaticus minor muscles and causes "crow's feet" around the eyes using the orbicularis oculi muscles.

Innervation

Like all muscles of facial expression, the risorius is innervated by the facial nerve (CN VII).

External links

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* [http://www.ptcentral.com/muscles/musclehead.html#risorius PTCentral]