The aorta carries oxygenated blood entering the systemic circulation. The blood from the heart enters the aorta through the aortic valve in the ascending aorta. With each heartbeat three leaflets on the aortic valve open and close. This allows one-way flow of blood. Then, the descending thoracic aorta travels down through the chest. Its small branches supply blood to the ribs and some chest structures.Most of the major organs receive blood from branches of the abdominal aorta,which begins at the diaphragm.