What does the lymphatic system do?
Your lymphatic system has many functions. Its key functions include:
- Collecting excess fluid from your body’s tissues and returning it to your bloodstream. This supports healthy fluid levels in your body. Your lymphatic system also filters out waste products and abnormal cells from this fluid.
- Helping your body absorb fats. Most nutrients can travel through tiny openings (pores) in the walls of your capillaries, and your body can then absorb and use them. But certain fats and other molecules are too large to travel in this way. Your lymphatic system collects fluid from your intestines that contains these molecules and transports it back to your bloodstream.
- Protecting your body against invaders. Your lymphatic system is part of your immune system. It produces and releases lymphocytes (a type of white blood cell) and other immune cells. These cells look for and destroy invaders — such as bacteria, viruses, parasites and fungi — that may enter your body.
How does the lymphatic system work?
Every day, about 20 liters of plasma (the liquid part of your blood) flow out of tiny pores in the thin walls of your capillaries. Imagine water seeping out of a sponge. Where does this liquid go? It delivers oxygen and nutrients to the tissues surrounding each capillary. The tissues hungrily soak up all the nutrients while leaving behind waste (like a kid who finishes their food but leaves behind a pile of sticky napkins).
The plasma doesn’t mind cleaning up the mess — it picks up the waste and then returns to your bloodstream the same way it came, by flowing back through the pores in your capillary walls. Each day, about 17 liters of plasma return to your bloodstream in this way. Since 20 liters initially flowed out of your capillary walls, that means 3 liters are still roaming around in your body’s tissues.
That’s where your lymphatic system steps in. Tiny lymphatic capillaries pick up this remaining fluid from your tissues. The fluid changed its name during its journey: now instead of plasma, it’s called lymph. Your lymphatic capillaries move the lymph into larger tubes called lymphatic vessels.
These vessels keep the lymph moving until it ultimately reaches one of two major ducts in your upper chest. These are called your right lymphatic duct and thoracic duct, and they’re a bit like highway on-ramps. They merge into large veins called your subclavian veins and empty the lymph into them. From there, your lymph reenters your bloodstream and can flow through your body again.
