Anterior intercostal arteries (anatomy)

The anterior intercostal arteries are derived from different sources depending on the interspace:

• upper six spaces: two branches on each side extending laterally from the respective internal thoracic artery
• seventh to ninth intercostal spaces: musculophrenic artery, a branch of the internal thoracic, gives off two anterior intercostal arteries in each interspace
• tenth and eleventh interspace: no anterior intercostal arteries; supplied solely by the posterior intercostal arteries

Where anterior intercostal arteries are present, they pass in a plane between the innermost intercostals and the inner intercostal muscles:

• one branch travels near to the inferior margin of the superior rib
• one branch travels near to the superior margin of the inferior rib At their origin, the anterior intercostal arteries of all but the most superior two interspaces also lie superficial to the transversus thoracis muscles.

Both sets anastomose with equivalent intercostal arteries posteriorly derived from either the:

• superior intercostal arteries for the most superior two interspaces, or
• thoracic aorta for the remaining inferior intercostal spaces

The anterior intercostal arteries supply perforating branches throughout their passage to supply:

• intercostal muscles
• pectoral muscles
• breasts
• superfical skin