2nd constriction in oesophagus is seen at the following site -
Where it crosses left main bronchus
Crossing of aorta
At pharyngoesophageal junction
Where it pierces the diaphragm
There are 4 esophageal constrictions. They are at 15cms, 22.5cms, 27.5cms and 37.5 to 40 cms, from the incisors. The second constriction is due to crossing of arch of aorta.