<prompt> Structures at Angle of LouisArch of aoaAzygous veinCommon carotid aeryClavicle  <response>: Sternal angleLouis angle:It is felt as a transverse ridge about 5cm below the suprasternal notch.It marks the manubriosternal joint and lies at the level of the second costal cailage anteriorly and the disc between the fouh and fifth thoracic veebrae posteriorly.This is an impoant landmark for many reasons.The arch of aoa begins and also ends at this level. BD CHAURASIAS HUMAN ANATOMY UPPER LIMB THORAX SIXTH EDITION VOLUME 1.PAGE NO187 