Thoracic part of esophagus

The thoracic part of esophagus is the longest segment of the esophagus and extends from the superior thoracic aperture to the esophageal hiatus of the diaphragm at the level of the T10 vertebra.

Location

• Initially, it lies within the superior mediastinum, positioned between the trachea anteriorly and the vertebral column posteriorly (slightly to the left of the median plane). As it descends, it passes posterior to and to the right of the arch of the aorta, entering the posterior mediastinum.

• In the lower thorax, it courses along the right side of the descending thoracic aorta, before gradually crossing anterior to the aorta and slightly to its left as it approaches the diaphragm.

• It enters the abdominal cavity through the esophageal hiatus at the T10 vertebral level. Immediately proximal to the diaphragmatic opening, the esophagus exhibits a slight fusiform dilatation known as the phrenic ampulla (ampulla epiphrenica).

Anterior relations of thoracic part of esophagus

Anteriorly, the thoracic part of esophagus is related successively to the trachea, the left main bronchus, the pericardium covering the left atrium, and finally the diaphragm. These relationships are of considerable clinical importance because enlargement of the left atrium may compress the esophagus and produce dysphagia.

Posterior relations of thoracic part of esophagus

Posteriorly, the thoracic esophagus rests upon the vertebral bodies, the longus colli muscles in its upper part, the right posterior intercostal arteries arising from the thoracic aorta, the thoracic duct, and the hemiazygos veins. Near the diaphragm, the descending thoracic aorta comes to lie directly posterior to the esophagus.

Important anatomical relations on the left side of thoracic esophagus

The left side of the thoracic esophagus displays important relations that vary with vertebral level. In the superior mediastinum, it is related to the terminal part of the arch of the aorta, the left subclavian artery, the thoracic duct, and the left mediastinal pleura. The left recurrent laryngeal nerve ascends in the groove between the trachea and esophagus, making it vulnerable during esophageal and mediastinal surgery.

Important anatomical relations on the right side of thoracic esophagus

Inferiorly, the esophagus lies in close contact with the descending thoracic aorta. On the right side, it is related to the right mediastinal pleura and the azygos vein, which arches over the root of the right lung before draining into the superior vena cava.

Relationship between esophagus and vagus nerves

Below the roots of the lungs, the vagus nerves come into intimate relationship with the esophagus. The right vagus nerve passes posterior to the esophagus, while the left vagus nerve lies anterior to it. Their branches interweave to form the esophageal plexus, from which the anterior and posterior vagal trunks are formed before passing through the diaphragm. These vagal fibers provide parasympathetic innervation to the esophagus and contribute to gastrointestinal innervation distal to the diaphragm.

Relationship with the thoracic duct

The thoracic duct also has an important relationship with the thoracic esophagus. In the lower posterior mediastinum, it lies on the right side of the esophagus. As it ascends, it passes posterior to the esophagus and crosses from right to left at approximately the level of the T4 vertebra, continuing superiorly along the left side of the esophagus into the root of the neck. The thoracic duct injury during esophageal surgery may result in a chylothorax.

Constrictions along the course of thoracic esophagus

Several normal constrictions are found along the thoracic esophagus. The first thoracic constriction occurs where it is crossed by the arch of the aorta (T4), followed by a second constriction produced by the left main bronchus (T5). A third constriction is present at the esophageal hiatus (T10).

Clinical correlates

• Esophageal carcinoma may invade adjacent structures such as the trachea, bronchi, pericardium, or aorta because of the close mediastinal relations of the thoracic esophagus.

• Left atrial enlargement may compress the esophagus, causing difficulty swallowing.

• The left recurrent laryngeal nerve may be affected by esophageal tumors, resulting in hoarseness due to vocal cord paralysis.

• Injury to the thoracic duct during esophageal surgery can lead to chylothorax.

• The aortic and bronchial constrictions are common sites for foreign body impaction and corrosive injuries.