Expansion
Posterior intercostals from the aorta; anterior intercostals from the internal thoracic and musculophrenic arteries
Expansion
Posterior intercostal arteries
- Spaces 1 and 2 - superior intercostal artery, from the costocervical trunk
- Spaces 3 to 11 - directly from the descending thoracic aorta
- Below rib 12 - the subcostal artery
Anterior intercostal arteries
- Spaces 1 to 6 - from the internal thoracic artery
- Spaces 7 to 9 - from the musculophrenic artery
- Spaces 10 and 11 - no anterior intercostal artery
Because each space is supplied from both ends, the anastomosis between them is a potential collateral channel. In aortic coarctation this pathway enlarges and the dilated, tortuous posterior intercostal arteries erode the undersurface of the ribs to produce rib notching.