Anatomical significance of the sternal angle
At this height is the intervertebral disk between the fourth and fifth thoracic vertebrae.
At this height, the trachea branches off into right and left bronchi.
At this height the aortic arch begins (the transition zone between the ascending aorta -> aortic arch)
At this height the aortic arch ends (aortic arch -> thoracic aorta transition)
The second costal cartilage is attached to both sides of this position on the sternum.
   The sternal angles are easily palpable in vivo and can be used as a guide to count the ribs (intercostal space). The Y coordinates of the trunk are provided.