Skeletotopy and spatial curves
The thoracic esophagus has a length of 15–18 cm and is projected from the level of Th II to Th XI. In its projection, the organ is not a perfectly straight tube. Due to the compliant peri-esophageal tissue, it forms variable curves in two planes.
In the sagittal plane, the esophagus initially follows the curvature of the vertebral column. It is separated from the vertebrae by the prevertebral fascia and a layer of connective tissue containing the azygos and hemiazygos veins (v. azygos, v. hemiazygos), the thoracic duct, and the right posterior intercostal arteries. Below the level of Th IV and then at the level of Th VIII–IX (the second sagittal curve), the organ gradually deviates anteriorly from the spine by a distance of 1.5–4.0 cm, lying anterior to the thoracic aorta (aorta thoracica).
In the frontal plane, the tube deviates to the left up to Th IV, then returns to the midline, and at the level of Th VIII makes another leftward curve.
Syntopy in the superior mediastinum
In the superior mediastinum, the esophagus forms the retrotracheal segment. It is located strictly posterior to the trachea, but due to the frontal curve, it slightly protrudes from beneath its left margin.
Key landmarks and topographic relationships:
- At the level of the tracheal bifurcation, the organ lies closely apposed on the left to the posterior-right surface of the aortic arch (arcus aortae). The aorta leaves a noticeable impression on the wall — the aortic constriction.
- On the left, the esophagus borders the initial segments of the left common carotid (a. carotis communis sinistra) and left subclavian (a. subclavia sinistra) arteries. The thoracic duct (ductus thoracicus) runs between these major vessels.
- In the tracheoesophageal groove on the left side runs the left recurrent laryngeal nerve (n. laryngeus recurrens sinister).
Important surgical aspect: short but large arterial branches arise from the aorta in the peri-esophageal tissue at the level of the bifurcation. Their inadvertent injury during organ mobilization threatens profuse hemorrhage.
Syntopy in the posterior mediastinum
Here, the esophagus transitions into the retropericardial segment. Descending below the aortic arch, it rests upon the posterior surface of the left principal bronchus (bronchus principalis sinister) and is fixed to it by strong connective tissue esophagotracheal ligaments.
The relationship with the descending aorta changes throughout its course: initially, the esophagus lies to the right of the vessel, then (at the level of Th IV–VIII) crosses the aorta obliquely, passing from anterior-right to left. By the level of Th IX, it is already located 1.0–1.5 cm to the left of the midline.
Anteriorly, below the tracheal bifurcation, the organ together with its fascial sheath adheres to the posterior wall of the pericardium, which anatomically separates it from the left atrium. This is of clinical significance: fluid accumulation (effusion) in the pericardial cavity can compress the esophagus, causing dysphagia. In addition, careless instrumental bougienage carries a high risk of pericardial perforation.
Relation to the pleura and the lymphatic system
The interaction with the mediastinal pleura is asymmetric. On the left, the pleura contacts the peri-esophageal fascia only in a small area between the descending aorta and the pulmonary ligament. On the right, below the root of the lung, it covers the lateral and partially posterior wall of the organ.
Below the hila of the lungs, the pleural folds of both sides converge posterior to the esophagus, forming the interpleural ligament. In the supradiaphragmatic region, this ligament, consisting of two layers (anterior and posterior), fuses tightly with the endothoracic fascia and fixes the organ to the crura of the diaphragm and the posteroinferior angles of the pleural recesses. Excessive tension on this ligament during esophageal mobilization can tear the mediastinal pleura and provoke a life-threatening bilateral pneumothorax.
The lymphatic system of the organ is represented by abundant intramural capillary networks. Lymph drainage is zonal in nature:
- From the upper sections, lymph drains primarily into the right and left paratracheal nodes (nodi lymphatici paratracheales).
- From the middle sections — into tracheobronchial (n.l. tracheobronchiales), bifurcation, and prevertebral nodes.
- From the lower sections, drainage occurs directly into the thoracic duct (ductus thoracicus), as well as toward the stomach (pericardial and left gastric nodes) and into peri-aortic nodes.
Briefly: answers to topical questions
Where does the right recurrent laryngeal nerve run in relation to the esophagus?
The right recurrent laryngeal nerve (n. laryngeus recurrens dexter) runs in the right tracheoesophageal groove, located between the trachea and the esophagus. It branches off from the right vagus nerve at the level of crossing the right subclavian artery (a. subclavia), loops around it inferiorly and posteriorly, after which it lies in the specified groove and ascends to the larynx. The nerve is the primary motor nerve of the larynx and innervates its muscles, as well as the mucosa below the vocal folds.
Which arteries supply the thoracic part of the esophagus?
The thoracic esophagus is supplied by branches of the thoracic aorta and the left gastric artery.
- Esophageal branches of the aorta (rr. esophagei aortae) — arise from the thoracic part of the aorta (pars thoracica aortae), run and branch along the walls of the esophagus. At the level of the tracheal bifurcation, short and large arteries arise from the aorta.
- Left gastric artery (a. gastrica sinistra) — supplies the lower thoracic esophagus.
Which nerves form the esophageal plexus?
The esophageal plexus (plexus oesophageus) is formed by branches of the vagus nerves, sympathetic trunks, and spinal nerves.
Its formation involves:
- Vagus nerves (nn. vagi) — the right and left vagus nerves give off branches that form the basis of the plexus in the posterior mediastinum.
- Sympathetic trunks (trunci sympathici) — give off sympathetic fibers from their thoracic ganglia.
- Spinal nerves — give off corresponding branches to the plexus.
The plexus is located in the peri-esophageal tissue on the esophagus (from the level of the tracheal bifurcation to the diaphragm), from where nerves penetrate the thickness of the organ wall, forming intramural networks.
What anatomical constrictions are distinguished in the esophagus?
The esophagus has three anatomical constrictions.
They are located at the following levels:
- First constriction — located at the pharyngoesophageal transition (at the level of the cricoid cartilage), situated at a distance of 12–15 cm from the incisors.
- Second constriction (aortic constriction) — located in the middle part of the esophagus, where it is adjacent to the aortic arch.
- Third constriction — located where the esophagus passes through the esophageal hiatus of the diaphragm.
Where does venous drainage from the thoracic esophagus occur?
Venous drainage from the thoracic esophagus occurs into the azygos vein system and the left gastric vein.
- Azygos vein system (v. azygos) — collects venous blood from the mid-thoracic esophagus.
- Left gastric vein (v. gastrica sinistra) — provides venous drainage from the lower thoracic esophagus.
The veins of the lower thoracic (esophagogastric) region participate in the formation of a portosystemic anastomosis, which is of great clinical importance in variceal veins.
Class and exam questions
Where exactly is the left recurrent laryngeal nerve located?
The left recurrent laryngeal nerve runs in a specialized groove between the left circumference of the esophagus and the trachea.
What is the clinical significance of the close proximity of the esophagus to the pericardium?
When pathological fluid accumulates in the pericardial sac, mechanical compression (constriction) of the esophagus can occur. In addition, blind bougienage carries a risk of perforation of the posterior wall of the pericardium.
Why is there a high risk of pneumothorax during dissection of the supradiaphragmatic part of the esophagus?
In the supradiaphragmatic region, the esophagus is firmly fixed by dense bundles of the two-layered interpleural ligament to the pleural recesses. If it is severely stretched during surgery, pleural rupture may occur, leading to the development of a bilateral pneumothorax.
What else to study on this topic
- Structure of the periesophageal space: topography of fasciae and posterior mediastinal tissue.
- Innervation of the esophagus: branches of the vagus nerves (n. vagus) and formation of the esophageal plexus.
- Sympathetic innervation of the esophageal tube by branches of the sympathetic trunks (truncus sympathicus).
- Detailed anatomy of the blood supply to the esophagus by branches of the thoracic aorta (pars thoracica aortae).
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