In human anatomy, the thoracic duct is an important part of the lymphatic system — it is the largest lymphatic vessel in the body. 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.
In adults, the thoracic duct is typically 38-45cm in length. It usually starts from the level of the second lumbar vertebra and extends to the neck.
It originates in the abdomen from the confluence of various abdominal lymph vessels. It extends vertically in the chest and curves posteriorly to the left carotid artery and left jugular vein to empty into the junction of the left subclavian vein and left jugular vein, near the shoulders. It traverses the diaphragm at the aortic aperture and ascends the posterior mediastinum between the descending thoracic aorta (to its left) and the azygos vein (to its right).
In human anatomy, the thoracicduct is an important part of the lymphatic system—it is the largest lymphatic vessel in the body.
The lymph transport in the thoracicduct is mainly caused by the action of breathing, aided by the duct's smooth muscle and by internal valves which prevent the lymph from flowing back down again.
When the thoracicduct is blocked or damaged a large amount of lymph can quickly accumulate in the pleural cavity, this situation is called chylothorax.
Opposite the fifth thoracicvertebra, it inclines toward the left side, enters the superior mediastinal cavity, and ascends behind the aortic arch and the thoracic part of the left subclavian artery and between the left side of the esophagus and the left pleura, to the upper orifice of the thorax.
The thoracicduct, at its commencement, is about equal in diameter to a goose-quill, but it diminishes considerably in caliber in the middle of the thorax, and is again dilated just before its termination.
The thoracicduct has several valves; at its termination it is provided with a pair, the free borders of which are turned toward the vein, so as to prevent the passage of venous blood into the duct.
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