<prompt> The cricopharyngeal sphincter is how far from the central incisor?15cm25cm40cm50cm  <response>: Ans. is a i.e., 15 cm Oesophagus shows four contrictions -i At the beginning at C6 vertebra, the first constriction of the cricopharyngeal sphinctor- 15 cm 6 inches from incisorii At the level of T4 vertebra where it is crossed by the aortic arch :-22.5 cm 9inches from the incisor.iii At the level of T6 vertebra where it is crossed by left principal bronchus 27.5 cm 11 inches from incisoriv At the level of T10 vertebra, its passage through esophageal hiatus of diaphram lower esophageal sphincter:- 37.5-40 cm 15-16 inches from incisor 