Understanding the Lymphatic System
The treatment of lymphedema is based on an understanding of how the lymphatic system works. Therapists must understand this system in depth. Patients, and others involved in self-care steps, need to have at least a basic understanding of these functions. It is this basic level of understanding that is presented here.
The functioning of the lymphatic system is closely related to that of the circulatory system. To understand more about how these systems differ, see The Circulatory and Lymphatic Systems Compared.
The Origin of Lymph
Lymph originates as blood plasma. The plasma of arterial blood is rich in “groceries” for the cells. In the capillary beds throughout the body the flow of blood is slowed so that plasma can leave and become tissue fluid. Tissue fluid is also known as intercellular fluid or interstitial fluid.
- Tissue fluid delivers the nutrients, oxygen, and hormones required by the cells.
- Tissue fluid collects and carries away some cellular waste products.
- 90 percent of the tissue fluid returns to the capillary bed. Here it again becomes plasma and continues its journey throughout the body as part of the venous circulation.
- Lymph is the 10 percent of the tissue fluid that is left behind. Normally the amount of lymph circulating in the body is one to two quarts and it makes up one to three percent of the body weight .
The Role of Lymph
The role of tissue fluid is to deliver the groceries to the cells. The role of lymph is to take out the trash that is left behind and to dispose of it.
As lymph continues to circulate between the cells it collects waste products that were left behind including dead blood cells, pathogens, and cancer cells. This clear fluid also becomes protein-rich as it absorbs dissolved protein from between the cells.
The lymphatic capillaries form a mesh-like network of tiny tubes that are distributed throughout the tissue spaces and are located just under the skin. These capillaries branch and interconnect freely so that they extend into almost all tissues.
Lymph capillaries are blind-ended tubes with no opening to allow the lymph easy access. The end of the capillary is only one-cell in thickness and these cells are arranged in a slightly overlapping pattern – like the shingles on a roof.
Pressure from the fluid surrounding the capillary forces these cells to separate for a moment. This allows fluid to enter, but not to leave, the capillary.
There are one-way valves within the lymphatic capillaries. These valves ensure the continued flow of the lymph away from the tissues.
This animation, which shows this action, was provided courtesy of John Ross, Senior Teaching Fellow, University of Luton, UK.
Deeper within the body the lymphatic vessels become progressively larger and are located near the veins. Like veins, the lymphatic vessels have valves to prevent any backward flow. Angions are the segments created by the space between two sets of valves. Smooth muscles in the walls of the lymphatic vessels cause the angions to contract sequentially to aid the flow of lymph toward the thoracic region.
At birth there are between 600-700 lymph otes present in the average human. Although these nodes can incease or decrease in size thoughout life, any nodes that have been damaged or destroyed, do not regenrate.
Afferent lymphatic vessels carry lymph into the nodes where waste products and some of the fluid are filtered out.
Lymphocytes, which are specialized white blood cells located within the lymph node, kill pathogens that may be present. Lymph nodes also trap cancer cells and slow the spread of the cancer until they are overwhelmed by it.
Efferent lymphatic vessels carry lymph out of the node to continue its return to the circulatory system.
Cancer cells that have left their original site travel first to nearby lymph nodes. For this reason lymph nodes play an important role in the detection and treatment of cancer.
The terminus is the area at the base of the neck where the lymphatic ducts return the lymph to the circulatory system.
Here the subclavian veins, which are located just under the collar bones, receive the lymph and it once again circulates throughout the body as plasma.
Drainage AreasLymphatic drainage is organization into two separate and very unequal drainage areas. These are the right and left drainage areas and normally lymph does not drain across the invisible lines that separate these areas. Structures within each area carry lymph to its destination, which is to return to the circulatory system.
The Right Drainage Area removes lymph from the:
- Right side of the head and neck
- Right arm
- Upper right quadrant of the body.
Lymph from this area flows into the right lymphatic duct. This duct returns the lymph to the circulatory system by draining into the right subclavian vein.
The Left Drainage Area removes lymph from the:
- Left side of the head and neck
- Left arm and the left upper quadrant
- Lower trunk
- Both legs
The cisterna chyli temporarily stores lymph as it moves upward from the lower areas of the body. The thoracic duct carries lymph upward to the left lymphatic duct. The left lymphatic duct returns the lymph to the circulatory system by draining into the left subclavian vein.
Why This is so Important
- Damage disturbs the flow. When lymphatic tissues or lymph nodes have been damaged, destroyed or removed, lymph cannot drain normally from the affected area. When this happens excess lymph accumulates and results in the swelling that is characteristic of lymphedema.
- Drainage areas. The treatment of lymphedema is based on the natural structures and the flow of lymph. The affected drainage area determines the pattern of the manual lymph drainage (MLD) and for self-massage. Although lymph does not normally cross from one area to another, MLD stimulates the flow from one area to another. It also encourages the formation of new lymph drainage pathways.
- MLD treatment and self-massage begin by stimulating the area near the terminus and the larger lymphatic vessels. This stimulates the flow of lymph that is already in the system and frees space for the flow of the lymph that is going to enter the capillaries during the treatment. See Lymphedema Treatment Methods.
- MLD treatment continues as a gentle massage technique to stimulate the movement of the excess lymph in affected tissues. The rhythmic, light strokes of MLD provide just the right pressure to encourage this excess lymph to flow into the lymph capillaries.
- The compression garments, aids, and/or bandages that are worn between treatments help control swelling by providing pressure that is needed to encourage the flow of lymph into the capillaries. See Compression Methods.
- Exercise is important in the treatment of lymphedema because the movements of the muscles stimulate the flow of the lymph into the capillaries. Wearing a compression garment during exercise also provides resistance to further stimulate this flow.
- Self-massage, as prescribed by your therapist, is another way in which lymph is encouraged to flow into the capillaries. Each self-massage session begins with steps to stimulate the flow of lymph that is already in the system. This is followed by gentle strokes are used to encourage the flow of lymph into the capillaries.
*** This information does not replace the advice of a qualified health care professional.