To better understand dissecting thoracic aneurysm, it helps to understand the anatomy of the aorta.

The aorta is the largest artery in the body. It starts at the heart and ends in the abdomen, where it branches into the iliac arteries. The thoracic aorta is the part of the aorta that resides in the chest.

The aorta is divided into three main segments:

• Aortic arch: originates at the heart and supplies the coronary arteries.
• Thoracic aorta: provides numerous branches, the intercostal arteries, which supply the chest wall.
• Abdominal aorta: supplies the gut and then terminates in the iliac vessels, which supply the pelvis and lower extremities.