The aorta is a very well designed tube that must convert chaotic flow (the blood ejected from the heart) into an organized stream. Imagine people leaving a sporting event or a concert: there is initial chaos, but eventually lines form at the exit and people proceed out the door. In much the same manner, two sites of chaos exist in the aorta. The first is at the aortic root, where blood shoots out of the heart and must be "corralled" into an organized manner. This active changing of the chaotic energy to organized flow requires strength. If the strength layer of the aorta is dysfunctional, the stress may internally break the aorta (a type A Dissection). The second site of chaos is at the end of the aortic arch, where blood must loop around and head downwards to supply the abdomen and legs. The turn that the blood makes in the aortic arch is also a very chaotic and energetic phenomenon. Consequently, the aorta may tear at this juncture as well (a type B dissection).