The subcostal arteries are the final pair of parietal branches produced by the thoracic aorta. They are located under the last ribs; however, they remain in sequence along with the aortic intercostal arteries. A posterior branch which behaves similarly as the posterior branch produced by an ordinary aortic intercostal artery is produced by each one of them.
Alongside the last thoracic nerve, the trunk goes towards the lower border of the twelfth rib. It goes towards the abdomen under the arcus lumbocostalis lateralis, and then anteriorly towards the quadratus lumborum, and posterior towards the colon and the kidney. It then enters the aponeurosis of beginning of the transversus abdominis, and also goes in between the transversus and the internal oblique muscles, anastomosing along with the sections of the superior epigastric artery, with the lumbar arteries, and also along with lower intercostal arteries.
The subcostal artery circulates some muscles within the walls of the thorax along with abdomen. The artery produces a dorsal section the circulation of which resembles that of the equivalent sections of the posterior intercostal arteries.