Thoracic duct

The thoracic duct is the largest lymphatic vessel of the lymph system. It is also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal.

In adults, the thoracic duct is typically 38-45cm in length and has an average diameter of 3mm-5mm. The vessel usually starts at the level of the second lumbar vertebra and extends to the root of the neck. It drains into the systemic (blood) circulation at the left venous angle. It collects most of the lymph in the body other than from the right thorax, arm, head and neck, which are drained by the right lymphatic duct.

The thoracic duct originates in the abdomen from the confluence of several lymphatic trunks: the right and left lumbar trunks and the intestinal trunk. This confluence is called the cisterna chyli. It traverses the diaphragm through the aortic aperture and ascends through the posterior mediastinum between the descending thoracic aorta (to its left) and the azygos vein (to its right). The thoracic duct extends vertically in the chest and curves posteriorly to the left carotid artery and left internal jugular vein at the C7 vertebral level to empty into the junction of the left subclavian vein and left jugular vein (the left venous angle, below the clavicle).