The aorta is the blood vessel that exits the heart and takes blood to the rest of the body. There is a valve between the aorta and the heart called the aortic valve.
Immediately above the valve are three outpouchings called the aortic sinuses from which the blood vessels to the heart arise. The remainder of the aorta is divided into three parts, the ascending aorta in the front, the aortic arch that gives off the blood vessels to the head and the descending aorta that travels on the left side of the spine.
The descending aorta travels through the diaphragm into the belly to become the abdominal aorta.