Chapter 2, Page 4  

NORMAL ANATOMY, EMBRYOLOGY, AND HISTOLOGY OF THE ESOPHAGUS Topographic Relationships and Normal Constrictions of the Esophagus A knowledge of the relationship of the esophagus to neighboring structures is important, since tumors in these structures can affect the esophagus, and vice versa (21). Cervical Esophagus. At its origin the esophagus lies on the vertebral bodies and is immediately posterior to the trachea. In the lateral grooves between the esophagus and trachea are the recurrent laryngeal nerves and adjacent to them are the right and left carotid sheaths and their contents. The lobes of the thyroid gland overlap the esophagus at the sides. At the root of the neck, on the left side of the esophagus, is the thoracic duct, which arches laterally behind the carotid sheath. Thoracic Esophagus. Up until the bifurcation of the trachea (roughly around the fifth thoracic vertebra), the esophagus lies posterior to the trachea. At this point the trachea veers to the right and the esophagus is covered by the left main bronchus (fig. 2-1) and below this by the pericardium and left atrium. In the lowermost portion of the thorax the esophagus passes behind the diaphragm and into the esophageal hiatus. On the left side of the esophagus, in the upper thoracic region, lies the ascending segment of the left subclavian artery and the parietal pleura. Below this, at the level of the fourth thoracic vertebra, is the arch of the aorta which then runs alongside the esophagus until the eighth thoracic vertebra. The descending aorta then passes behind the esophagus (fig. 2-3). At this point the pleura is again in contact with the esophagus. On the right side the pleura lies adjacent to the esophagus along most of its length. Posteriorly the thoracic portion of the esophagus lies on the thoracic vertebrae up to the point where the descending aorta passes behind the esophagus. The azygos vein lies behind and to the right of the esophagus running up to the fourth thoracic vertebra; then it turns forward (fig. 2-4). The thoracic duct ascends on the right side of the lower esophagus. At the level of the fifth thoracic vertebra it passes behind the esophagus and then continues upwards on the left side, to the cervical esophagus. Abdominal Esophagus. This is a very short segment which lies on the diaphragm, with the liver anterior to it. Normal Constrictions. Normally, a number of indentations and constrictions can be found in the esophagus due to impingement from adjacent structures. These are potential sites at which food and pills may become lodged. These indentations occur at the following sites: at the level of the cricoid cartilage, caused by the cricopharyngeus muscle; at the aortic arch; at the level of the left atrium, where the left main bronchus crosses the esophagus; and at the diaphragmatic opening. Below the tracheal bifurcation the esophageal plexus of nerves and anterior and posterior vagal nerves are close to the esophagus.