The aorta is the heart's main artery. It carried blood from the heart to all parts of the body.
It is often considered to have 5 sections (see diagram):
The aortic root
The part nearest the heart, attached to the aortic valve and the opening of the heart's own arteries (the coronary arteries).
The ascending aorta
The initial part of the aorta where the blood is being pumped upwards from the heart.
The aortic arch
The aorta loops over and descends. The loop is known as the aortic arch. Many major arteries, including those supplying the brain, branch off the aorta at this point.
The descending aorta
The portion of the aorta which descends until it reaches the diaphragm.
The abdominal aorta
The remainder of the aorta, now passing down inside the abdominal region.