Risorius
| Risorius | |
|---|---|
| File:Sobo 1909 260 - Risorius.png Superficial muscles of the head and neck, showing the risorius in red. This version of the muscle does not match that shown in most sources. | |
| File:Musculusrisorius.png Muscles of the head, face, and neck. Risorius shown in red. This is the most standard version of the direction and origin of the muscle. | |
| Details | |
| Origin | Parotid fascia |
| Insertion | Modiolus |
| Artery | Facial artery |
| Nerve | Buccal branch of the facial nerve |
| Actions | Draws back angle of mouth |
| Identifiers | |
| Latin | musculus risorius |
| TA98 | Lua error in Module:Wikidata at line 746: attempt to index field 'wikibase' (a nil value). |
| TH | {{#property:P1694}} |
| TE | {{#property:P1693}} |
| FMA | {{#property:P1402}} |
| Anatomical terms of muscle [[[d:Lua error in Module:Wikidata at line 865: attempt to index field 'wikibase' (a nil value).|edit on Wikidata]]] | |
The risorius muscle is a highly variable muscle of facial expression. It has numerous and very variable origins, and inserts into the angle of the mouth. It receives motor innervation from branches of facial nerve (CN VII). It may be absent or asymmetrical in some people. It pulls the angle of the mouth sidewise, such as during smiling.
Structure
[edit | edit source]The risorius muscle is highly variable.[1]
Attachments
[edit | edit source]Its peripheral attachments may include (some or all of): the parotid fascia, masseteric fascia, the fascia enveloping the pars modiolaris of the platysma muscle, fascia overlying the mastoid part of temporal bone, and/or the zygomatic arch.[1]
Its apical and subapical (i.e. convergent) attachment is at the modiolus.[1]
Innervation
[edit | edit source]The risorius receives motor innervation from the buccal branch of the facial nerve (CN VII).[1]
Vasculature
[edit | edit source]The risorius receives arterial supply mostly from the superior labial artery.[1]
Variation
[edit | edit source]The risorius muscle is highly variable. It ranges in form from one or more slender bundles to a wide (yet thin) fan.[1] It may be absent in a significant minority of people, and may be asymmetrical.[2]
Relations
[edit | edit source]It is superficial to the masseter muscle, partially overlying it.[3]
Function
[edit | edit source]The risorius muscle draws the angle of the mouth lateral-ward.[1] It participates in producing facial expressions like a smile,[4] grin, or laugh.[1]
Clinical significance
[edit | edit source]Because it partially overlies the masseter muscle, it may be unintentionally affected during botox injections, resulting in unnatural facial expressions.[3]
Other animals
[edit | edit source]It has been suggested that the risorius muscle is only found in Homininae (African great apes and humans).[5]
Etymology
[edit | edit source]From the Latin word rīsor (“laugher, mocker”) + -ius (adjectival suffix).
A great way to remember the function of the resorius muscle is by remmebering that its name literally translates to "the laughing muscle".
Additional images
[edit | edit source]-
Position of risorius.
References
[edit | edit source]Public domain This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)
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External links
[edit | edit source]
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