The Thoracic Duct is the largest lymphatic vessel in the body. It originates with the Cisterna Chyli between T11 and L2. It perforates the diaphragm and runs up to the left venous angle where it joins the left subclavian vein. (The left jugular trunk, supraclavicular trunk, subclavian trunk and the parasternal trunk connect near the thoracic trunk at the left venous angle). There is a valve at the junction of the thoracic duct and the left subclavian vein that prevents the reflux of blood into the lymphatic system. Approximately 3 litres of lymph transported up the thoracic duct enters the blood circulation at this point.
Length: 36 – 45 cm
Width: 1 – 5 mm
The thoracic duct drains the lymph from 75% of the body, aside from the right upper right limb, right breast, right lung and right side of the head and neck (which are drained by the right lymphatic duct).