What is the lymphatic system?

What is the lymphatic system?
Just as most people don’t know much about their spleens, they also know very little about their lymphatic system. Perhaps it’s no surprise that the two are related? Both the spleen and the lymphatic system (with its vessels and nodes) play an important role in our immune response to disease and infections. Not to sound the hysteria alarm here, but without our lymphatic systems, we’d all turn into elephants, develop horrible infections and die.

What do elephants have to do with this? Well, as I discussed in a recent health tip about what can cause leg swelling,  I reminded us that a rare cause of leg swelling is damage to the lymphatic system. This damage is often caused unintentionally as a side effect of surgery, trauma, or radiation treatments. In some countries, tiny parasites are introduced into the body via mosquito bites, and they multiply inside the lymph vessels and nodes until they block them off completely. This results in a condition known as “elephantiasis” because the chronic back up of fluid into the extremities makes the legs look deformed and swollen – almost like an elephant leg. You can see a severe example at this website here.

The lymph system has two main roles: to remove excess fluid that the veins didn’t capture and to circulate immune cells (called white blood cells) to fight infection and remove infectious debris from the tissues. You may have noticed swollen glands (or lymph nodes) in your neck when you had a throat infection. This is a good example of how the body attacks and clears infection – white blood cells are delivered to the site of a bacterial or virus invasion (such as your throat) and they kill the bad guys. Then the lymph system suctions up the liquid mess, sometimes transporting live cells and viruses to the next relay station (called a lymph node). If the infection war is still raging, the lymph node itself can become a swollen and tender battle ground. In the end, the lymph fluid is dumped into the bloodstream through neck veins and the body cleans the blood via the liver  and kidneys.
If you look at the drawing of the lymphatic system (picture above), you can see that it is spread throughout the entire body, so it can fight infections wherever they may crop up. Lymph nodes are mostly located deep inside the body and can’t be felt with the finger tips. Neck, arm pit, and groin lymph nodes are exceptions – and this is why checking for swollen nodes in these areas are part of a doctors’ physical exams.
So what does the spleen have to do with this? The spleen is considered to be part of the immune system because one of its functions is to produce white blood cells. These cells circulate in the lymphatic system, but they are manufactured in the spleen (and tonsils, intestinal wall, thymus gland, and bone marrow too.)
What can go wrong with the lymphatic system?
  1. Mechanical damage can disrupt the flow of lymph fluid, causing fluid back up and swelling.  The lymph vessels are very delicate (almost like spider webs), and their walls are not as tough as arteries or veins. They are therefore quite prone to injury by mechanical and compressive forces. The most common causes of lymphatic system injury are surgery, radiation, and trauma. Luckily the lymphatic system is a complex web that can usually find flow work-arounds. However, if there is extensive damage in a specific area, it can be overwhelming and result in swelling to the nearby limb (for example) previously served by that part of the system.
  2. Cancer can plug up the system or cancer treatment can damage the lymphatics.  When white blood cells divide out of control and become cancerous, it makes sense that they can damage the circulatory lymph system where they live. Lymphoma is a cancer of the lymph system that directly damages it. Sometimes cancer spreads through the lymph system and travels to other parts of the body. When cancer gets into the lymph nodes, physicians sometimes have to cut those nodes out (lymph node dissections are common in breast cancer treatment, for example) or use radiation to burn the cancer. This can lead to chronic swelling issues in the arms or legs, known as lymphedema.
  3. Parasites can block the lymphatic system.  As discussed earlier, certain parasitic worms have an affinity for the lymph system and although they can be killed with medicines, the damage they do to the lymph vessels and nodes may be permanent.
How do you keep the lymph system healthy?
  1. Regular exercise can help to reduce the amount of tissue edema and swelling that the veins and lymph system need to clear.
  2. Treat lymph system damage early.  If you have swelling in an arm or leg from previous injury or cancer treatment, make sure you get treatment early. Reducing the length of time that the lymph system is over-taxed may decrease the long term damage. Kind of like a hernia – you should get it fixed sooner rather than later or it will just expand and get worse.
  3. Avoid tight fitting clothes.  If you have lymphatic issues, compressing the area with tight clothing will only make things worse.
  4. Physical therapy.  Some physical therapists (PTs) specialize in treating lymphedema. They have developed excellent massage techniques that can help to “milk” the lymph back to the blood circulation (called manual lymph drainage). They can also provide special wraps to reduce arm and leg swelling.

In my experience, physical therapy provides the very best treatment for lymphedema. With regular wrapping and manual lymph drainage, even elephant-like limbs can be returned to near-normal size. So although I raised a fairly scary prospect of life without our lymphatic system (in paragraph one), those who do have damage to their lymph systems should be encouraged: lymphedema specialist PTs will not let you become an elephant!

If you have any more questions just Ask Hanna, our health advisors are here to help.
Image: ©Shutterstock / sciencepics

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