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Internal intercostal muscles

Group of muscles between the ribs

Summary

Group of muscles between the ribs

Field	Value
Name	Internal intercostal muscles
Latin	musculi intercostales interni
Image	Internal intercostal muscles back.png
Caption	Internal intercostal muscles (red) seen from back.
Caption2	Deep muscles of the chest and front of the arm, with the boundaries of the axilla (the internal intercostal muscles are labeled as Intercostalis internus at bottom left)
Origin	Rib - superior border
Insertion	Rib - inferior border
Action	Hold ribs steady
Antagonist	External intercostal muscles
Blood	Intercostal arteries
Nerve	Intercostal nerves

The internal intercostal muscles (intercostales interni) are a group of skeletal muscles located between the ribs. They are eleven in number on either side. They commence anteriorly at the sternum, in the intercostal spaces between the cartilages of the true ribs, and at the anterior extremities of the cartilages of the false ribs, and extend backward as far as the angles of the ribs, hence they are continued to the vertebral column by thin aponeuroses, the posterior intercostal membranes. They pull the sternum and ribs upward and inward.

Structure

Their fibers are also directed obliquely, but pass in a direction opposite to those of the external intercostal muscles. The internal intercostal muscles originate from the costal groove of the rib and insert into the superior aspect of the rib below in a direction perpendicular to the external intercostal muscles. It is this arrangement that allows these muscles to facilitate exhalation.

For the most part, they are muscles of exhalation. In exhalation the interosseous portions of the internal intercostal muscles, (the part of the muscle that is between the bone portion of the superior and inferior ribs), depresses and retracts the ribs, compressing the thoracic cavity and expelling air. The internal intercostals, however, are only used in forceful exhalation such as coughing or during exercise and not in relaxed breathing. The external intercostal muscles, and the parasternal part of the internal intercostal muscles, (the part of the muscle that lies between the cartilage portion of the superior and inferior ribs), are used in inspiration, by aiding in elevating the ribs and expanding the thoracic cavity.

Additional images

File:Internal intercostal muscles animation.gif|Position of internal intercostal muscles (red). Animation. File:Gray395.png|The obliquus internus abdominis. File:Gray846.png|Thoracic portion of the sympathetic trunk.

References

Tang A, Bordoni B. Anatomy, Thorax, Muscles. [Updated 2020 Jul 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538321/
Basic Human Anatomy - O'Rahilly, Müller, Carpenter & Swenson{{page needed. (May 2015)
Anatomy and Physiology: The Unity of Form and Function 5th Edition by Kenneth Saladin{{page needed. (May 2015)
"The Action of the Internal Intercostals". www.yorku.ca.

Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

muscles-of-the-torso

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