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Thoracic Duct (Left Lymphatic Duct)

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Last updated: Sep 17th, 2025
Thoracic Duct (Left Lymphatic Duct)
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The thoracic duct, or the left lymphatic duct, is the largest of the body's lymphatic ducts. It collects almost all of the lymph that circulates throughout the body (the remainder is collected by the right thoracic duct); from there, the lymph flows back into the bloodstream. The thoracic duct is a structure roughly sixteen inches long located in the mediastinum of the pleural cavity which drains lymph fluid from everywhere except the upper right quarter of the body above the diaphragm and down the midline (this is collected by the right lymphatic duct).