Muscle · Chest

External intercostals

Musculi intercostales externi

Eleven pairs of short muscles filling the spaces between the ribs, their fibres running downward and forward from each rib to the one below — the same direction as the external oblique, which they continue into. They lift the ribs during inhalation, swinging each one up and out so the rib cage widens as the diaphragm drops. Clinically they are the tissue behind the founder's phrase 'rib cage stiffness': if the spaces between the ribs will not lengthen, the lower ribs cannot swing out, the breath goes up into the chest, and the neck muscles inherit the work.