<prompt> Which of the following structures is related to the esophagus 22.5cm from the incisor teeth?Arch of aortaRight principal broncusThoracic DuctAzygous Vein  <response>: Ans. is a i.e., Arch of aorta 2nd constriction is at T4 level where arch of aorta crosses esophagus.Esophageal constrictionsNumberDistance from incisorBony levelAnatomical landmark1st15 cm 6 inchesC6At its beginning pharyngo-esophageal junction2nd22.5 cm 9 inchesT4Crossing of aortic arch3rd27.5 cm 11 inchesT6Crossing of left main bronchus4th37.5 - 40 cm 15-16 inchesT10Piercing diaphragm at lower esophageal sphmotor 