Editing Intercostal muscles

{{short description|Muscle groups between the ribs which form and move the chest wall during breathing}}
{{one source|date=March 2021}}
{{Infobox muscle
| Name        = Intercostal muscles
| Latin       = musculi intercostales
| Image       = Intercostal-muscle.jpg
| Caption     = Intercostal muscles highlighted in dark red.
| Image2      =
| Caption2    =
| Origin      = Ribs 1–11
| Insertion   = Ribs 2–12
| Blood       = [[Intercostal arteries]]
| Nerve       = [[Intercostal nerves]]
| Action      = Elevation or depression of the ribs

}}
The '''intercostal muscles''' comprise many different groups of [[muscle]]s that run between the [[ribs]], and help form and move the [[chest wall]]. The intercostal muscles are mainly involved in the mechanical aspect of [[breathing]] by helping expand and shrink the size of the [[chest cavity]].<ref>{{Cite web|date=2020-01-10|title=Intercostal muscle strain: Signs, treatments,remedies|url=https://www.medicalnewstoday.com/articles/320925|access-date=2021-02-28|website=www.medicalnewstoday.com|language=en}}</ref>

==Structure==
There are three principal layers:
# [[External intercostal muscles]] also known as intercostalis externus aid in quiet and forced [[inhalation]]. They originate on ribs 1–11 and have their insertion on ribs 2–12. The external intercostals are responsible for the elevation of the ribs and bending them more open, thus expanding the transverse dimensions of the [[thoracic cavity]]. The muscle fibers are directed downwards, forwards and medially in the anterior part.
# [[Internal intercostal muscles]] also known as intercostalis internus aid in forced [[Exhalation|expiration]] (quiet expiration is a passive process). They originate on ribs 2–12 and have their insertions on ribs 1–11.Their fibers pass anterior and superior from the upper margin of the rib and costal cartilage to the lower margin of the rib above.<ref name=Dartmouth>[https://www.dartmouth.edu/~humananatomy/part_4/chapter_20.html (source)] {{Webarchive|url=https://web.archive.org/web/20171206060551/http://www.dartmouth.edu/~humananatomy/part_4/chapter_20.html |date=2017-12-06 }}</ref> The internal intercostals are responsible for the depression of the ribs and bending them inward, thus decreasing the transverse dimensions of the thoracic cavity. The muscle fibers are directed downwards, forwards and laterally forming right angle with external intercostal muscle.
# [[Innermost intercostal muscle]] also known as intercostalis intimus are deep layers of the internal intercostal muscles which are separated from them by a [[neurovascular bundle]]. The muscle fibers are directed downwards, forwards and laterally same as intercostalis internus muscle.<ref name=":0">{{Cite book |last=Datta |first=AK |title=Essentials of Human Anatomy |publisher=Current Books International |year=2018 |isbn=978-93-85274-37-4 |edition=10th |location=India |pages=21 |language=en}}</ref>

===Nerve supply===
Both the external and internal muscles are innervated by the [[intercostal nerves]]<ref name=":0" />(the [[ventral rami]] of [[thoracic spinal nerves]]), are supplied by the [[intercostal arteries]], and are drained by the [[intercostal veins]]. Their fibers run in opposite directions.

==Function==
The [[scalene muscles]], which also move the chest wall and have a function in inhalation, are also intercostal muscles, just not one of the three principal layers.

==See also==
{{Anatomy-terms}}
* [[Thoracic diaphragm]], another muscle importantly involved in respiratory action.
* [[Exhalation]]
* [[Inhalation]]

==References==
{{Reflist}}

==External links==
{{Commons}}
* {{SUNYAnatomyFigs|18|03|03}}
* [https://web.archive.org/web/20160303230510/http://faculty.ucc.edu/biology-potter/Musculature/sld020.htm UCC]
* [[iarchive:GraysAnatomy41E2015PDF|Gray's Anatomy 41st Edition]]

{{Muscles of thorax and back}}

[[Category:Muscles of the torso]]