What is the source of the lower intercostal and subcostal arteries?

The lower intercostal and subcostal arteries originate from the aorta, specifically the thoracic aorta as it descends in the thoracic cavity. This is significant because the intercostal arteries supply blood to the muscles and tissues of the thorax, vital for respiratory movements. The aorta is the main artery of the body and provides branches that ensure adequate blood supply to various regions, including the lower intercostal spaces.

In contrast, other arteries such as the internal thoracic artery primarily supply the anterior chest wall and are not the source of the lower intercostal or subcostal arteries. Similarly, the inferior and superior epigastric arteries are branches of the external iliac artery and internal thoracic artery, respectively, and they supply the anterior abdominal wall rather than the intercostal spaces. Therefore, the aorta is clearly the correct source for these specific arteries.