Internal intercostal muscles

Intercostales interni muscle
Deep muscles of the chest and front of the arm, with the boundaries of the axilla. (Intercostalis internus labeled at bottom left.)
Posterior surface of sternum and costal cartilages, showing Transversus thoracis. (Intercostalis internus visible at left.)
Latin	musculi intercostales interni
Gray's	subject #117 403
Origin	rib - inferior border
Insertion	rib - superior border
Artery	intercostal arteries
Nerve	intercostal nerves
Actions	hold ribs steady
Antagonist	Intercostales externi muscles

The Intercostales interni (Internal intercostals) are eleven in number on either side. They commence anteriorly at the sternum, in the interspaces 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, whence they are continued to the vertebral column by thin aponeuroses, the posterior intercostal membranes.

Each arises from the ridge on the inner surface of a rib, as well as from the corresponding costal cartilage, and is inserted into the lower border of the rib above.

Their fibers are also directed obliquely, but pass in a direction opposite to those of the Intercostales externi.

Additional images

A central rib of the left side. Inferior aspect.

The Obliquus internus abdominis.

Diagram of the course and branches of a typical intercostal nerve.

Thoracic portion of the sympathetic trunk.

External links

• LUC inin
• -254803891 at GPnotebook
• SUNY Labs 18:03-0101 - "The Internal Intercostal Muscle"
• SUNY Figs 18:03-03 - "Transverse section of thorax."
• internal+intercostal+muscle at eMedicine Dictionary

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated.

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