It is entirely contained within the , a protective sac that also encloses the heart . It lies behind the pulmonary artery and the sternum and is adjacent to the superior vena cava . Structural Composition
: This initial portion starts at the aortic annulus and contains the aortic valve and the sinuses of Valsalva . ascending aorta
: This part extends from the sinotubular junction to the beginning of the aortic arch at the level of the sternal angle . It is entirely contained within the , a