Aortic Arch

The arch of the aorta is the part of the aorta that begins at the level of the upper border of the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left side of the trachea and finally passes downward on the left side of the body of the fourth thoracic vertebra, at the lower border of which it becomes continuous with the descending aorta.

It thus forms two curvatures: one with its convexity upward, the other with its convexity forward and to the left. Its upper border is usually about 2.5 cm. below the superior border to the manubrium sterni. The upper curvature has a region of higher pressure that forces blood flow to the upper regions of the body that are located above the heart (arms, neck, and head). The lower curvature of the arch has a lower pressure than the upper curvature, and this is where the ductus arteriosus is connected during the fetal stage, allowing the high pressure flow of blood from the right ventricle to mostly bypass the pulmonary vessels as they develop (they are still fluid filled).