Internal intercostal

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Intercostal muscle
Deep muscles of the chest and front of the arm, with the boundaries of the axilla.
Gray's	subject #117 403
Origin	ribs 1-11
Insertion	ribs 2-12
Artery	{{{Blood}}}
Nerve	intercostal nerves
Action
MeSH	Intercostal+Muscles

Intercostal muscles are several groups of muscles that run between the ribs, and help form and move the chest wall.

There are three principal layers;

• the external intercostal muscles, which 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 expanding the transverse dimensions of the thoracic cavity.

Located around the ribs

• the internal intercostal muscles, which aid in forced expiration (quiet expiration is a passive process). They originate on ribs 1-11 and have their insertions on ribs 2-12. The internal intercostals are responsible for the depression of the ribs decreasing the transverse dimensions of the thoracic cavity.
• the innermost intercostal muscle, the deep layers of the internal intercostal muscles which are separated from the them by the neurovascular bundle.

Both the external and internal muscles are innervated by the intercostal nerves (the ventral rami of thoracic spinal nerves), and are provided by the intercostal arteries and intercostal veins. Their fibers run in opposite directions.

[edit] Other intercostal muscles

Besides the scaleni, which also move the chest wall and have a function in inhalation, other intercostal muscles are:

• Subcostal muscles
• Transversus thoracis muscle

[edit] External links

• -294977459 at GPnotebook
• SUNY Figs 18:03-03
• UCC

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