Both these tuberosities and the intra trabecular groove, provide attachment to different muscles that we will name, later on Distal or inferior to these tuberosities the shaft continues and at the point where the shaft becomes narrower around this location where I am pointing with my pencil is often referred to as the surgical neck of the humerus and it has clinical importance because of arteries that surround the humerus at this location and because of the. 