Where do lymphatic vessels ultimately return interstitial fluid to the venous circulation?

• A. External jugular veins
• B. Subclavian veins
• C. Superior vena cava
• D. Aorta

Answer: (B)

Lymphatic fluid is returned to the venous blood at the junctions where the lymphatic ducts meet the venous system, near the venous angles formed by the union of the internal jugular and subclavian veins. This means the final entry point is at the subclavian veins (the thoracic duct draining into the left venous angle and the right lymphatic duct into the right venous angle). The other vessels listed aren’t where lymph returns: external jugular veins are superficial drainage, the superior vena cava is downstream from the entry point, and the aorta is an arterial vessel. So, the subclavian veins are the correct site for returning interstitial fluid to the bloodstream.