It collects most of the lymph in the body (except that from the right arm and the right side of the chest, neck and head, which is collected by the right lymphatic duct) and drains into the systemic (blood) circulation at the left subclavian vein.
Location and direction of flow
It extends vertically in the chest and curves posteriorly to the left carotid artery and left jugular vein at the C7 vertebral level to empty into the junction of the left subclavian vein and left jugular vein, below the clavicle, near the shoulders.
Volume, mechanism, and direction of flow
In adults, the thoracic duct transports up to 4 L of lymph per day.
The lymph transport in the thoracic duct is mainly caused by the action of breathing, aided by the duct's smooth muscle and by internal one way valves which prevent the lymph from flowing back down again.
There are also two valves at the junction of the duct with the left subclavian vein, to prevent the flow of venous blood into the duct.
The first sign of a malignancy (especially an intraabdominal one) may be an enlarged Virchow's node, a lymph node in the left supraclavicular area, in the vicinity where the thoracic duct empties into the left subclavian vein.
It is also known under various other names including the alimentary duct, chyliferous duct, duct of Pecquet, the left lymphatic duct and Van Hoorne's canal. 
Transverse section of thorax, showing relations of pulmonary artery.
The arch of the aorta, and its branches.
Deep lymph nodes and vessels of the thorax and abdomen (diagrammatic).
The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind.
- Template:SUNYAnatomyFigs - "The thoracic duct and azygos venous network."
- Diagram at anatomyatlases.org