The external intercostals are the inspiratory intercostal muscles, running obliquely forward and downward. Their oblique direction produces a net rib-elevating force during contraction (the bucket handle movement), expanding the thoracic volume.
| Origin | Lower border of each rib — from the tubercle to the costochondral junction |
|---|---|
| Insertion | Upper border of the rib immediately below — posterior fibre direction (like hands in front pockets) |
| Nerve Supply | Intercostal nerves (T1-T11) |
| Blood Supply | Posterior and anterior intercostal arteries |
| Actions | Elevate the ribs during inspiration — the primary muscles of quiet inspiration; Stabilise the intercostal spaces against inward movement |
|---|
External intercostal blocks (intercostal nerve blocks) provide unilateral chest wall analgesia — the nerve runs in the subcostal groove beneath the rib between the internal and innermost intercostals. VATS surgery preserves the external intercostals by using the intercostal space rather than rib spreading.
Not directly palpable individually — the intercostal space can be palpated between ribs.
Rib fracture disrupting the external intercostals producing paradoxical chest wall movement in flail chest, managed by rib plating to restore chest wall mechanics.
