Anatomy of Lymphatics

Abstract

To facilitate a clearer understanding of the topographical arrangement of lymphatics, pictorial demonstrations based on actual cadaveric dissections of four segments of the digestive tract (esophagus, stomach, colon, and rectum) are provided.

• 1. The lymphatics of the esophagus: Due to the pressure of the aortic arch from the left, asymmetrical development of the ascending lymphatics along the trachea and esophagus is observed. The typical right ascending lymphatic chain reaches the lower neck and follows upstream along the inferior thyroid artery to reach the right venous angle. Several branches are given off from this chain at various levels to finally reach the venous angle. As the left ascending chain is generally poorly developed, most of the lymphatics of the left tracheobronchial nodes move rightward to join the right chain. The left chain is located close to and anterior to the left recurrent laryngeal nerve. The lymphatic chain of the lower thoracic esophagus connects with the lymph vessels of the left gastric nodes via the superior diaphragmatic nodes close to the esophagus.

• 2. The lymphatics of the stomach: In general, lymphatics accompany the typical arteries and finally connect to the coeliac nodes at the origin of the coeliac trunk. However, in the case of the right gastroepiploic artery, lymph vessels do not accompany the artery, but rather they run along the vein and drain into the superior mesenteric nodes. Furthermore, atypical lymphatics are observed: (a) those which descend along the posterior gastric artery to join the splenic lymphatics, and (b) those which run along the cardioesophageal branch of the left inferior phrenic artery, and then descend along this artery, to finally drain into the lateral aortic nodes.

• 3. The lymphatics of the colon: The lymphatics of the right hemicolon accompany the colic branches of the superior mesenteric artery and then gather around this artery. Before reaching the superior mesenteric artery, lymph vessels cross the superior mesenteric vein. The lymphatics of the left hemicolon also run along the inferior mesenteric artery and gather at the lateroaortic nodes. Some lymph vessels cross in front of the abdominal aorta and reach the interaorticocaval nodes.

• 4. The lymphatics of the rectum: In addition to the classically recognized superior group, the lateral (middle) group of the lymphatics are demonstrated. In order to reach the subaortic nodes, lymphatics from the rectum first reach the nodes of the interiliac area with or without accompanying the middle rectal artery. The iliac lymph vessels surround and run alongside the iliac blood vessels. Before reaching the interiliac area, the lymphatics cross over or under the cord of the umbilical artery. Some lymph vessels from the posterior wall of the rectum run backwards and pierce the fascial membrane between the right and left hypogastric nerves before reaching the subaortic nodes. The subaortic nodes are of great importance as they perform the role of a terminal station of the pelvic lymphatics as well as the starting station of the para-aortic lymphatics.

• 5. The para-aortic nodes (lumbar nodes): Para-aortic nodes surround not only the abdominal aorta, but also the inferior vena cava. The para-aortic lymphatics originate from the subaortic nodes and from the lateral aortic and lateral caval nodes at the level of the lower ends of the aorta and inferior vena cava. These lymphatics are also well developed behind the two great blood vessels. Up to the level of the renal blood vessels, the lymphatics surrounding the inferior vena cava gather around the interaorticocaval nodes. The lymph vessels from the uppermost interaorticocaval and lateral aortic nodes converge behind the aorta to form the thoracic duct.