Abstract
PURPOSE: The thoracic duct uses the pulsation of accompanying arteries to facilitate lymphatic flow. However, the lymphatic flow mechanism cannot be explained when it does not accompany the arteries. This study aimed to clarify the anatomical position of the thoracic duct and surrounding structures and determine the differences in the thoracic duct length and course during inspiration and expiration. METHODS: Six cadavers were dissected to observe the positional relationship between the thoracic duct and surrounding structures. Image sequences of anatomical sections from the Visible Korean Human Open Resource were observed and reconstructed to understand their three-dimensional positioning. Inspiratory and expiratory computed tomography scans were used to measure and examine respiratory variations in the distance between the arterial landmarks to predict the thoracic duct length. RESULTS: The thoracic duct accompanied the arteries for most of its course and was sandwiched between the arteries and pleura, entering the mediastinum. However, there was an area on the cranial side of the aortic arch where the thoracic duct did not accompany the arteries. The distance between the arterial landmarks in this area, which approximate the thoracic duct length, was significantly longer during inspiration (39.3 ± 7.81 mm) than during expiration (31.49 ± 7.01 mm). CONCLUSION: This study suggests that the pleura entering the mediastinum pushes the thoracic duct toward the arteries to promote lymphatic flow generation by arterial pulsation. Additionally, this study suggests that the lymphatic flow in the thoracic duct is generated by the expansion and contraction of the thoracic duct with respiratory movement.