The oesophagus begins at the lower edge of the cricoid cartilage, opposite the lower border of the sixth cervical vertebra, and ends at the cardiac opening of the stomach, opposite the eleventh thoracic vertebra.

It is 25 cm. (10 in.) long and begins 15 cm. (6 in.) distant from the teeth. In the neck it inclines to the left, hence oesophagotomy is performed on that side. It reaches the farthest point to the left at the level of the top of the sternum or opposite the second thoracic vertebra. It then inclines to the right, reaching the median line opposite the fifth thoracic vertebra. It then again inclines to the left, to pierce the diaphragm in front of the aortic opening and to the left of the median line opposite the tenth thoracic vertebra, and ends in the cardiac opening of the stomach entirely to the left of the median line and opposite the eleventh thoracic vertebra or tenth dorsal spine. In its passage through the diaphragm it is accompanied by the continuation of the two vagi nerves. At its termination it grooves the posterior surface of the liver. Lumen. - The lumen of the oesophagus is narrowed at three points, (1) its commencement; (2) where it crosses the aorta and left bronchus; and (3) near its end as it passes through the diaphragm.

The average diameter of the lumen is 2 cm., which at the upper and lower constrictions is reduced to 1.5 cm. The middle constriction is not quite so marked. The lower constriction is most marked at the point of the passage of the oesophagus through the diaphragm; it enlarges slightly as it enters the stomach. This part of the oesophagus is quite distensible. The next most distensible part is opposite the left bronchus. This is on a level with the middle of the first piece of the sternum and the third thoracic vertebra. The upper constriction at the cricoid cartilage is the least distensible part of the tube, so that a body passing it may pass entirely down.

In both living and dead bodies the lumen of the oesophagus is sometimes open and sometimes closed. In the neck the pressure of the soft parts usually keeps it closed, but frozen sections of the dead body show it sometimes closed and sometimes open. Mikulicz in using the oesophagoscope has found the lumen open in the living patient and been able to see down the remainder of the tube when the instrument has only been passed beyond the second constriction.

In passing an oesophageal bougie, one should not be used of a larger diameter than 18 mm. (3/4 in.). It will enter the oesophagus opposite the lower border of the cricoid cartilage about 15 cm. (6 in.) from the teeth. It will pass the second constriction 7 cm. (2 3/4 in.) farther on, opposite the middle of the first piece of the sternum or 2.5 cm. (1 in.) below its upper border, and meet the third constriction 15 cm. (6 in.) lower down, or 37 cm. (14.4 in. ) from the teeth, and enter the stomach 3 cm. below, or 40 cm. (16 inches) from the teeth and opposite the eleventh dorsal vertebra.