By Doctor Sanjoy Kundu The aorta is the largest artery in your body,and it carries blood away from your heart. Your aorta runs through your chest, where it is called the thoracic aorta. When it reaches your abdomen, it is called the abdominal aorta. The abdominal aorta supplies blood to the lower part of the body. Just below the abdomen, the aorta splits into two branches that carry blood into each leg. When a weak area of the abdominal aorta expands or bulges, it is called an abdominal aortic aneurysm (AAA). The pressure from blood flowing through your abdominal aorta can cause a weakened part of the aorta to bulge, much like a balloon. A normal aorta is about 2 centimeters in diameter. However, AAA can stretch the aorta beyond its safety margin.