Intercostal muscles

Intercostal muscles are many different groups of muscles 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.[1]

Intercostal muscles
Intercostal muscles highlighted in dark red.
Details
Originribs 111
Insertionribs 212
Arteryintercostal arteries
Nerveintercostal nerves
ActionsElevation or Depression of the Ribs
Identifiers
LatinMusculi intercostales
MeSHD007366
FMA13354
Anatomical terms of muscle

Structure

There are three principal layers;

  1. External intercostal muscles aid in quiet and forced inhalation. They originate on ribs 111 and have their insertion on ribs 212. 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.
  2. Internal intercostal muscles aid in forced expiration (quiet expiration is a passive process). They originate on ribs 212 and have their insertions on ribs 111.Their fibers pass anterior and superior from the upper margin of the rib and costal cartilage to the lower margin of the rib above.(source) The internal intercostals are responsible for the depression of the ribs and bending them inward, thus decreasing the transverse dimensions of the thoracic cavity.
  3. Innermost intercostal muscle, the deep layers of the internal intercostal muscles which are separated from them by a neurovascular bundle.

Nerve supply

Both the external and internal muscles are innervated by the intercostal nerves (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

References

  1. "Intercostal muscle strain: Signs, treatments,remedies". www.medicalnewstoday.com. 2020-01-10. Retrieved 2021-02-28.
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