This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
[{'content': 'Which of the following structures is related to the esophagus 22.5cm from the incisor teeth? \nSelect and explain. \nA. Arch of aorta, B. Right principal broncus, C. Thoracic Duct, D. Azygous Vein', 'role': 'user'}, {'content': "Answer: A \nExplanation: 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 inches)C6At its beginning (pharyngo-esophageal junction)2nd22.5 cm (9 inches)T4Crossing of aortic arch3rd27.5 cm (11 inches)T6Crossing of left main bronchus4th37.5 - 40 cm (15-16 inches)T10Piercing diaphragm (at lower esophageal sphmotor)", 'role': 'assistant'}]