<prompt> 2nd constriction of esophagus is caused by -Left bronchusArch of aortaDiaphragmLower sphincter  <response>: Ans. is b i.e., Arch of aorta o 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 sphinctor 