What is the main collecting duct for lymph?

• A. Jugular vein
• B. Thoracic duct
• C. Cisterna chyli
• D. Right lymphatic duct

Answer: (B)

Lymph from most of the body returns to the bloodstream through a single, large channel called the thoracic duct. It starts as a sac in the abdomen known as the cisterna chyli, which gathers lymph from the lower body and intestines, then ascends through the chest to empty into the left venous angle (the junction of the left internal jugular and left subclavian veins). The thoracic duct handles lymph from the left side of the head and neck, the left upper limb, the left chest, and essentially everything below the diaphragm, making it the main collecting duct for lymph. The right lymphatic duct, in contrast, handles only the right side of the head and neck, right upper limb, and right chest, draining into the right venous angle. The jugular vein is a blood vessel, not a lymphatic duct, so it isn’t involved in draining lymph.