Wednesday, November 10, 2010

The Lymphatic System

This is a concise view of the lymphatic system as viewed by western medicine. I wrote this article as part of the Anatomy and Physiology series on

The lymphatic system was not understood in the western world until as little as two decades ago, yet this system is responsible for keeping us healthy and vibrant on a daily basis. Problems from the simple cold to complex cancer are tied to the lymphatic system.

This article will focus entirely on the lymph system anatomy and then next Anatomy and Physiology article will focus more on the immune system function.

What is the Lymphatic System?
The lymphatic system is considered to be a part of the circulatory system. Like the cardiovascular system it is made up of various organs, vessels, and fluids.

 The lymphatic system has four functions:
  1. The removal of interstitial fluid from tissue spaces and then the circulation of this fluid (lymph) back into the blood stream
  2. The circulation of fatty acids to the blood stream
  3. The transportation of immune cells to and from the lymph nodes.
  4. The creation and circulation of lymphocytes, an important part of immune system function.

Problems in the lymphatic system can lead to swelling and even cancer. An impaired lymphatic system can also lead to an overall poor immune system and leave someone susceptible to various illnesses.

The lymphatic system is made up of the following organs, vessels and substances:

Interstitial fluid
As blood plasma is forced from the blood capillaries it gathers in the tissue spaces. Once the plasma is no longer within the venous system it is called the interstitial fluid. It is a watery-like substance that bathes the cells of the tissues.

Lymphatic capillaries
Lymphatic capillaries are completely immersed in the interstitial fluid. They have thin membranes that allow the interstitial fluid to flow in. Once the interstitial fluid is in these lymphatic capillaries we refer to it as lymph.  Like the venous system, the lymphatic system has a series of valves that only allow the lymph to move in one direction. The lymphatic capillaries are continuously draining the interstitial fluid from the tissue spaces. This prevents lymphatic stagnation or edema.

Lymphatic vessels
Lymphatic vessels are formed by the merging of the lymphatic capillaries. There are about the same amount of lymphatic vessels in the body as there are veins. Lymph continues to flow in one direction through these vessels. Eventually these lymphatic vessels merge to form larger structures called lymphatic trunks.

Lymphatic trunks
Lymphatic trunks are the largest lymphatic vessel in the body. They drain directly into two different lymphatic collecting ducts.

 Right lymphatic duct
The right lymphatic duct drains the lymphatic trunks from the right side of the head and neck, the right arm and shoulder and the ride side of the trunk or thorax. This duct is short and empties directly into the right subclavian vein.

Thoracic duct
The thoracic duct is responsible for collecting the lymph from the rest of the body including the legs, left arm and most of the trunk including the abdominals. It empties into the left subclavian vein.

As the lymph enters either the right or left subclavian vein it has been returned back to the blood stream where it can be either reused or filtered further by the liver, spleen and kidneys.

Organs of the Lymph System

 Lymph nodes
Also called lymph glands these organs are solely responsible for cleansing and filtering the lymph. They are located along the larger lymphatic vessels throughout the whole body. They tend to accumulate more heavily in the groin, arm pits, abdominals, and neck regions. Lymph nodes are somewhat bean shaped and are around 2mm in length. Lymph enters the node through the afferent lymphatic vessels. It continues to flow to the lymphatic sinus cavities. It is collected from there to continue its movement through the efferent lymphatic vessel. Through this process the lymph is filtered of cells that have been damaged, cancerous cells, cellular debris, and pathogens like bacteria and viruses.

The nodules located in the lymph nodes are the location of lymphocyte production. Lymphocytes along with macrophages destroy the waste materials that have been filtered in the lymph nodes. We will discuss more of this process when we look at the immune system function.

Many of us are probably familiar with the tonsils. These are important lymphatic organs that act as the guards to our internal body. Located near the throat or the back of the mouth and nasal cavities, these clumps of lymphatic tissue intercept and kill pathogens that enter through the nose or mouth. As little as twenty years ago these organs were routinely removed in children who repeatedly had problems with them swelling. Now, we have more understanding of the important function of these tissues and they are seldom removed.

The spleen is the largest organ of the lymphatic system. It can be found behind the stomach and just underneath the diaphragm. It is about 5-6 inches long and 2-3 inches wide. It, like all lymphatic organs, produces lymphocytes.

The spleen plays a role in both the lymphatic system and the cardiovascular system. It cleanses and filters the blood. The spleen can destroy harmful pathogens in the body and it is also the main site for red blood cell production. It stores a large supply of blood and platelets, which are released when needed, such as a hemorrhage.

It is not that uncommon to have a spleen removed. Those people without a spleen can live full lives, but they may be more susceptible to illness and hemorrhage.

Thymus gland
The thymus gland is a soft structure located in the mediastinum just above the heart. This gland plays a big role in the immune system development of infants and children. As we age, the gland begins to shrink and is actually quite small in adults. The major role of this gland is the production of a particular type of lymphocyte called T-cells. These important immune system cells can attack and destroy foreign antigens. We will look at T-cells more closely when we study the immune system.

I’ve heard it suggested that we can help to stimulate our thymus gland by pounding on our chests like gorillas or tarzan. This article explains further and gives 10 Ways to Jump Start Your Day.

How lymph moves
There are a lot of parallels between the lymphatic system and the cardiovascular system. Both of these involve circulating fluids throughout our body using very similar structures such as vessels. The lymphatic system differs in a major way in that it does not have a heart pumping fluid through its vessels. Instead lymph moves only with the help of outside forces.

These forces include:
Contraction of muscles
Respiration or the act of breathing

Just looking at this list and you can see how important movement and exercise are to maintaining a healthy lymphatic system. Some people suggest jumping on a trampoline or skipping jubilantly is one of the best ways to get lymph flowing.

Further Reading:

7Song’s pdf on An Herbalists View of the Lymph System

Fantastic article by Suzanne Sky explaining the lymphatic system and then giving detailed suggestions on personal lymphatic massage.

Paul Bergner has an excerpt from his fabulous book, The Healing Power of Echinacea and Goldenseal, that discusses several lymphatic herbs. Besides reading this short excerpt  I also highly recommend this book. Besides giving an incredible indepth view on two very important western herbs, it is also has a really thorough description of the immune system and how it functions.

This Love your Lymph article briefly looks at some lymphatic herbs and has great suggestions in how to keep your lymph healthy.

Kiva Rose discusses using alder trees as a lymphatic.

An article about Lymphatic Massage

Finally the Spleen Gets Some Respect, an interesting NYT articles highlighting a new understanding of the spleen and it’s functions.

Works Consulted
The anatomy and physiology in this article was extracted mainly from The Principles of Anatomy & Physiology, Tortora, Grabowski. I also used Anatomy and Physiology by Stanley E. Gunstream 4th ed.

The second half of this article giving us an herbal perspective on the nervous system would not have been possible without jim mcdonald’s Article Index. Thanks a thousand times to jim for putting this together.