Innermost intercostal muscle
Innermost intercostal muscle is a layer of intercostal muscles deep to the plane that contains the intercostal nerves and intercostal vessels and the internal intercostal muscles.
Origin:
Infero-posterior border of each rib (above).
Insertion:
Supero-posterior border of the rib (below).
Nerve supply:
intercostal nerves.
Blood Supply:
- Anterior intercostal artery
- posterior intercostal artery
- internal thoracic artery
- musculophrenic artery
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.
