Thoracic duct versus right lymphatic duct: drainage territories
Lymph (fluid leaked from capillaries) returns to the blood through two ducts: the thoracic duct drains most of the body, the right lymphatic duct only the right upper quarter.
Remember
The right lymphatic duct serves only the right upper limb, the right thorax and the right side of the head and neck, whereas the thoracic duct drains the rest of the body into the left subclavian vein (the vein from the arm).
Memory aid
picture the right upper quadrant as a small territory that has its own small drain, while everything else goes by the big duct
Here the right upper quadrant means the upper right quarter of the body, not the abdomen, which the big duct drains.
Fluid leaks from capillaries, and the lymphatic vessels (a one-way network running beside the blood vessels) collect it as lymph. Two ducts then return it to the blood by emptying into the veins at the base of the neck.
The right lymphatic duct is the smaller one. It collects lymph from the right upper limb, the right thorax and the right side of the head and neck, together called the upper right quadrant (the upper right quarter of the body). It empties into the right subclavian vein (the vein from the arm).
The thoracic duct is much larger and drains the rest of the body: both lower limbs, the abdomen, the left upper limb, and the left side of the thorax, head and neck. It begins in the abdomen at the cisterna chyli, a sac that gathers lymph from the intestinal trunk (from the gut) and two lumbar trunks (from the lower body); these trunks are collecting vessels for lymph. From there it climbs through the chest and empties into the left subclavian vein.
Each duct ends at a venous angle, the meeting point of the subclavian vein and the internal jugular vein (the vein from the head and neck) on its own side. Lymph can enter here because this is a low-pressure part of the circulation. So the right lymphatic duct ends at the right venous angle, and the thoracic duct ends at the left one, although the exact point of entry varies a little between people.
If a mass blocks the thoracic duct close to its end, lymph from the regions it drains backs up, and swelling (lymphoedema) can follow.
Key facts
- Right duct territory
- the right side of the head and neck, the right thorax and the right upper limb, which together make up the upper right quadrant.
- Thoracic duct territory
- the rest of the body, including both lower limbs, the abdomen, the left upper limb and the left side of the head and neck.
- Where the thoracic duct starts
- in the abdomen at the cisterna chyli, which receives lymph from the intestinal trunk and two lumbar trunks.
- Where each duct ends
- the right lymphatic duct at the right venous angle, in the right subclavian vein, and the thoracic duct at the left venous angle, in the left subclavian vein; the exact point of entry varies a little between people.
- Right breast
- lymph from the right side of the thorax, which includes the right breast, drains to the right lymphatic duct.
- Thoracic duct blockage
- a mass close to its end can make lymph from the lower limbs, abdomen, left upper limb, and left side of the thorax, head and neck back up, and swelling (lymphoedema) can follow.
Exam traps
- The thoracic duct does not empty into the right subclavian vein. It empties on the left, and drainage into the right subclavian vein belongs to the much smaller right lymphatic duct.
- The cisterna chyli does not enter the inferior vena cava, because lymph passes up through the thoracic duct first; the cisterna chyli is a step on the route, not the final entry.
- Lymph from the right leg and pelvis does not enter the right lymphatic duct: it travels through lymph nodes (such as the inguinal nodes, in the groin) and up the lumbar trunks to the cisterna chyli and the thoracic duct.
Read the full notes
Tested in 11 SimpleMed+ questions
Practice it in Pathology, with the answer and a full explanation after every question.
Practice these questions