Lymph Vessels of the Esophagus
The lymph vessels of the esophagus can be injected from the muscular layer as well as from the mucosa of the esophagus, however, the lymph vessels from both tissues in any given section of the esophagus usually drain to the same lymph nodes. These lymph vessels form very coarse networks in the submucosa; the networks are primarily composed of the lymph vessels of the mucosa, though the lymph vessels of the muscular layer also contribute to the network formation. Occasionally, a fine network was visible through the epithelium after dye injection, apparently located inside the mucosa. The small lymph vessels arising from the submucosal networks often travel relatively long distances between the mucous membrane and the muscles before penetrating the muscle and joining the lymph vessels of the muscles. Other lymph vessels of the mucous membrane penetrate the muscle layer directly and form coarse networks with the lymph vessels of the muscles in the adventitia, and in some cases in the muscles as well. The lymph vessels arising from the lymphatic networks drain to the medial retropharyngeal lymph node, the deep cervical lymph nodes, the cranial mediastinal lymph nodes, the tracheobronchial lymph nodes, the left hepatic lymph node, the splenic lymph nodes, and the gastric lymph node. A detailed description of their behaviour is as follows:
A. Lymph Vessels of the Cervical Esophagus
The lymph vessels of the cervical part of the esophagus (Figure 23: b, b) drain to the medial retropharyngeal lymph node (Figure 23: 1), the deep cervical lymph nodes (Figure 23: 2, 3, 4) and the cranial mediastinal lymph nodes (Figure 23: 6, 6’). From the initial part of the esophagus (approximately the cranial quarter of the cervical esophagus), the lymph vessels, usually 1 to 3, drain to the medial retropharyngeal lymph node (Figure 23: 1), and, if one is present, to the cranial cervical lymph node (Figure 23: 2). Drainage occurs to lymph nodes on both sides. Occasionally, one of the lymph vessels additionally drains to either the middle cervical (Figure 23: 3) or caudal cervical (Figure 23: 4) lymph nodes, or, in their absence, to a cranial mediastinal lymph node.
The path taken by the lymph vessels to the medial retropharyngeal lymph node is variable; either they run directly on the pharyngeal musculature to the lymph node (Figure 23: 5), or they initially run orally underneath the mucosa before passing through the pharyngeal musculature (usually at the angle between M. hyothyroideus and M. keratopharyngeus) (Figure 23: 5′), at times running along the medial side of the thyroid cartilage.
In 1 case, all the lymph vessels drained to a cervical lymph node located between the thyroid gland and the pharyngeal muscles, and none drained to the medial retropharyngeal lymph node, whereas in other cases, they drained into both lymph nodes.
In 2 of 7 cases examined, 1 lymph vessel from the initial part of the esophagus drained to a middle cervical or caudal cervical lymph node, while in another case, a lymph vessel drained to a cranial mediastinal lymph node.
Most of the lymph vessels from the middle one-third of the cervical esophagus (Figure 23) drain to the caudal cervical lymph node (Figure 23: 4) (and middle cervical lymph node on occasion [Figure 23: 3]), though some accompany the lymph vessels of the caudal section of the esophagus to drain to the cranial mediastinal lymph nodes (Figure 23: 6, 6’) (see below). In the absence of the cervical lymph nodes, all the lymph vessels drain to the mediastinal lymph nodes (Figure 23: 6, 6’).
In 8 other closely examined cases, an unpaired caudal cervical lymph node was found 3 times. This lymph node drained 1 to 2 lymph vessels that originated from the middle third of the cervical esophagus – these vessels were formed by the confluence of 3 to 4 single lymph vessels and travelled to the lymph node along either the left or right side of the trachea. In 1 case, 3 caudal cervical lymph nodes were present, and all 3 received lymph vessels from the middle third of the esophagus. In 2 cases, a left middle cervical lymph node was found, which also drained lymph vessels from the middle third of the cervical esophagus: in 1 of these cases, a right middle cervical lymph node was found as well, and it additionally drained lymph vessels from the esophagus. These latter vessels obviously crossed the median plane. In addition to all these lymph vessels, in 3 of the cases described above, an additional lymph vessel was found to emerge from the middle third of the cervical esophagus, joining the lymph vessels from the caudal part of the cervical esophagus and draining with them to the cranial mediastinal lymph nodes (Figure 23: 6). In the last 2 cases, the caudal cervical and middle cervical lymph nodes were absent, and all the lymph vessels drained to a mediastinal lymph node. They were always found to drain to a left mediastinal lymph node, either the left main mediastinal lymph node or to the mediastinal lymph node located on the left side of the cranial vena cava.
The lymph vessels of the caudal one-third of the cervical esophagus (Figure 23) drain to the cranial mediastinal lymph nodes (Figure 23: 6, 6’). A large number of tiny lymph vessels arise from this part of the esophagus and merge to form 1 to 2 larger vessels, which may also receive lymph vessels from the middle part of the cervical esophagus (see above), before entering the thoracic cavity along with the esophagus (on its two borders and two surfaces), through the thoracic inlet, and draining to a mediastinal lymph node. In the examined cases, the lymph vessels always drained to a left mediastinal lymph node, either the left main mediastinal lymph node (Figure 23: 6) or the lymph node located on the left side of the cranial vena cava (Figure 23: 6’).
In one case with 2 lymph vessels draining the caudal one-third of the cervical esophagus, one lymph vessel traveled around the right border of the trachea at the level of the 2nd intercostal space and passed over the ventral edge of the trachea to drain to the lymph node located on the left side of the cranial vena cava. The other lymph vessel traveled a relatively long distance (to the entrance of the thoracic cavity), between the mucous membrane and the fascia, penetrated the fascia, and ran from the left side of the esophagus to drain to the left cranial mediastinal lymph node.
B. Lymph Vessels of the Thoracic Esophagus
The lymph vessels of the thoracic esophagus drain to the mediastinal lymph nodes, the tracheobronchial lymph nodes, the left hepatic lymph node, the splenic lymph nodes, and the gastric lymph node. The lymph vessels of the esophagus in the cranial half of the thoracic cavity drain mainly to the mediastinal lymph nodes, in almost all cases to the left mediastinal lymph nodes, but occasionally also cross over the right side of the trachea to drain to the right mediastinal lymph nodes. Some of the lymph vessels also join the lymph vessels of the esophagus in the caudal half of the thoracic cavity, which enter the abdominal cavity with the esophagus and drain to either the left hepatic lymph node, a splenic lymph node, or the gastric lymph node (see lymph vessels of the stomach). I observed this latter behaviour particularly in the lymph vessels of the esophageal mucosa, but also in isolated cases of those of the fascia and of all the thoracic esophagus up to the thoracic inlet, so from the cranial third of the thoracic esophagus as well. These lymph vessels usually travel a relatively long distance between the mucous membrane and the fascia towards the diaphragm, and, when injected, may be visible through the musculature. They usually only penetrate the outer surface of the fascia very close to the diaphragm, and then join the lymph vessels of the caudal half of the thoracic esophagus (see below).
Some lymph vessels of the caudal half of the thoracic esophagus (Figure 18: t) drain into the tracheobronchial lymph nodes, specifically to the left and middle (Figure 18: 1) lymph nodes. However, most of the lymph vessels join with the lymph vessels of the cranial half of the thoracic esophagus (see above) and enter the abdominal cavity, through the diaphragm, with the esophagus as 4 to 7 lymph vessels, forming many networks. The vessels then run from the cardia, between the serosa and muscularis of the stomach. Some of the lymph vessels run to the small curvature of the stomach and from there in the dorsal wall of the omentum, more or less accompanied by the left gastric vein until reaching the splenic vein (Figure 28: 7), and drain into the left hepatic lymph node (Figure 28: 1). If a gastric lymph node is present at the small curvature of the stomach, some of these lymph vessels will first drain to it. The remainder of the lymph vessels run from the cardia, around its left side, to the gastrosplenic ligament (Figure 28: 7’), and travel in it to reach the splenic vein, draining to the splenic lymph nodes (Figure 28: 8).
The individual drainage areas of the thoracic esophagus are not sharply delineated from one another. Just as some of the lymph vessels from the cranial part of the thoracic esophagus drain to a left hepatic lymph node, it can happen that lymph vessels from the caudal part of the thoracic esophagus drain to a cranial mediastinal lymph node, or a lymph vessel from the cranial part of the thoracic esophagus drains to a tracheobronchial lymph node. It is also not uncommon for lymph vessels to pass from one part of the esophagus around either the dorsal or ventral borders of the esophagus to the other side: e.g. the lymph vessels labelled 5 in Figure 18, which drain to the left tracheobronchial lymph node.
