Descending aorta

The descending aorta is defined as the segment of the aorta that begins just distal to the origin of the left subclavian artery at the aortic arch and extends through the thoracic cavity (descending thoracic aorta) to the diaphragm, then continues as the abdominal aorta until its bifurcation into the common iliac arteries.

The wall of the descending aorta consists of three layers: the intima (a thin endothelial layer), the media (a thick layer of smooth muscle cells, elastic fibers, and collagen arranged in concentric lamellae), and the adventitia (a connective tissue layer containing the vasa vasorum and nerves). The descending thoracic aorta is maller in diameter than the ascending aorta, narrowing from approximately 2.5 cm proximally to 2.0 cm distally, with further reduction in the abdominal segment.

Branching from the descending thoracic aorta are the intercostal arteries, which supply the thoracic wall and spinal cord. The abdominal aorta gives rise to major visceral branches, including the celiac trunk, superior mesenteric artery, and inferior mesenteric artery, as well as paired renal and lumbar arteries.