The thoracic duct is the biggest lymphatic vessel in the human body, and plays a key role in the lymphatic system. It is also called the left lymphatic duct or the alimentary duct. A large part of the body's lymph is collected by this duct, and drained into the bloodstream near the brachiocephalic vein between the internal jugular veins and the left subclavian. The typical length of this duct in an adult averages between 38 and 45cm and the diameter is about 5mm. It originates from the second lumbar vertebra level and goes to the neck's root. The duct arises from the combination of the left and right lumbar trunks and the intestinal trunk in the abdomen. The thoracic duct gets extended in the chest area and from there it curves towards the internal jugular vein and the left carotid artery at the C7 vertebra. It travels through the aortic aperture diaphragm and rises along the posterior mediastinum. It carries up to four liters of lymph each day. This action is primarily caused by the breathing action and assisted by the smooth muscle of the duct.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Thoracic Duct