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Thoracic lymphatic duct
Other Terms: Trunk of thoracic duct tree, Ductus thoracicus, Conduit thoracique
The thoracic duct, or left lymphatic duct, is 38-45cm long (about 15 to 17 ½ inches) and about 5mm (half of a centimeter) in diameter. It is the largest lymphatic vessel in the body and transports up to 4 L of lymph per day. It begins at the level of the second lumbar vertebra at the cisterna chyli, enters the thorax through the aortic opening in the diaphragm, and runs upward posterior to the esophagus and to the right side of the aorta in the posterior mediastinum. It then passes through the superior mediastinum and leaves the thorax by passing through its upper opening and extends to the root of the neck. Behind the left internal jugular vein and common carotid artery and opposite the seventh cervical vertebra, the duct forms an arch above the subclavian artery and anterior to the vertebral artery and vein, and descends in front of the scalenus anterior muscle to empty into the left subclavian vein at its junction with the internal jugular vein. A double valve guards its entrance into the vein, preventing venous blood flow into the duct. The thoracic duct receives the lymph vessels from about three-fourths of the body: from the left side of the head, neck, and thorax, the left upper extremity, the abdomen, and the lower extremities. The duct can be described as consisting of three parts-abdominal, thoracic, and cervical.