| Innermost intercostal muscle | |
|---|---|
|   Innermost intercostal muscle (red), seen from back. | |
| Details | |
| Origin | Infero-posterior border of each rib (above) | 
| Insertion | Supero-posterior border of the rib (below) | 
| Artery | Intercostal arteries | 
| Nerve | Intercostal nerves | 
| Actions | Through adduction of upper ribs to the lower ribs the muscles narrow intercostal slits and diminish thorax volume, therefore the muscles represent expiratory muscles. | 
| Identifiers | |
| Latin | musculus intercostalis intimus | 
| TA98 | A04.4.01.014 | 
| TA2 | 2313 | 
| FMA | 74086 | 
| Anatomical terms of muscle | |
The innermost intercostal muscle is a layer of intercostal muscles. [1] It may also be called the intima of the internal intercostal muscles. [2] It is the deepest muscular layer of the thorax, [3] with muscle fibres running vertically (in parallel with the internal intercostal muscles). [2] It is present only in the middle of each intercostal space, and often not present higher up the rib cage. [3] It lies deep to the plane that contains the intercostal nerves and intercostal vessels, and the internal intercostal muscles. [3] [4] The diaphragm is continuous with the innermost intercostal muscle. [5]