The Lymphatic System

THE LYMPHATIC SYSTEM IS COOPERATIVE

Major lymphatic ducts. (Courtesy of NIH/NCI)

• The lymphatic system aids the immune system in removing and destroying waste, debris, dead blood cells, pathogens, toxins, and cancer cells.
• The lymphatic system absorbs fats and fat-soluble vitamins from the digestive system and delivers these nutrients to the cells of the body where they are used by the cells.
• The lymphatic system also removes excess fluid, and waste products from the interstitial spaces between the cells.

THE TRANSFORMATION

Arterial blood carries oxygen, nutrients, and hormones for the cells. To reach these cells it leaves the small arteries and flows into the tissues. This fluid is now known as interstitial fluid and it delivers its nourshing products to the cells. Then it leaves the cell and removes waste products.

After this task is complete, 90% of this fluid returns to the circulatory system as venous blood.

WHAT IS LYMPH?

The remaining 10% of the fluid that stays behind in the tissues as a clear to yellowish fluid known as lymph.

• Unlike blood, which flows throughout the body in a continue loop, lymph flows in only one direction within its own system. This flow is only upward toward the neck. Here, it flows into the venous blood stream through the subclavien veins which are located on either sides of the neck near the collarbones.
• After plasma has delivered its nutrients and removed debris, it leaves the cells. 90% of this fluid returns to the venous circulation through the venules and continues as venous blood.
• The remaining 10% of this fluid becomes lymph which is a watery fluid that contains waste products. This waste is protein-rich due to the undigested proteins that were removed from the cells.

LYMPHATIC CIRCULATION

The lymph is moved through the body in its own vessels making a one-way journey from the interstitial spaces to the subclavian veins at the base of the neck.

• Since the lymphatic system does not have a heart to pump it, its upward movement depends on the motions of the muscle and joint pumps.
• As it moves upward toward the neck the lymph passes through lymph nodes which filter it  to remove debris and pathogens. 
• The cleansed lymph continues to travel in only one direction, which is upward toward the neck.
• At the base of the neck, the cleansed lymph flows into the subclavian veins on either side of the neck. 

Lymph returning to the subclavian veins. © Lymph Notes

THE ORIGIN OF LYMPH

Lymph originates as plasma (the fluid portion of blood). The arterial blood, which flows out of the heart, slows as it moves through a capillary bed. This slowing allows some plasma to leave the arterioles (small arteries) and flow into the tissues where it becomes tissue fluid.

• Also known as extracellular fluid, this is fluid that flows between the cells but is not into the cells. This fluid delivers nutrients, oxygen, and hormones to the cells.
• As this fluid leaves the cells, it takes with it cellular waste products and protein cells.
• Approximately 90% of this tissue fluid flows into the small veins. Here it enters the venous circulation as plasma and continues in the circulatory system.
• The remaining 10% of the fluid that is left behind is known as lymph.

LYMPHATIC CAPILLARIES

In order to leave the tissues, the lymph must enter the lymphatic system through specialized lymphatic capillaries. Approximately 70% of these are superficial capillaries located near, or just under, the skin. The remaining 30%, which are known as deep lymphatic capillaries, surround most of the body’s organs.

Lymphatic capillaries begin as blind-ended tubes that are only a single cell in thickness. These cells are arranged in a slightly overlapping pattern, much like the shingles on a roof. Each of these individual cells is fastened to nearby tissues by an anchoring filament.

LYMPHATIC VESSELS

The lymphatic capillaries gradually join together to form a mesh-like network of tubes that are located deeper in the body.

• As they become larger, and deeper, these structures become lymphatic vessels.
• Deeper within the body the lymphatic vessels become progressively larger and are located near major blood veins.
• Like veins, the lymphatic vessels, which are known as lymphangions, have one-way valves to prevent any backward flow.
• Smooth muscles in the walls of the lymphatic vessels cause the angions to contract sequentially to aid the flow of lymph upward toward the thoracic region. Because of their shape, these vessels are previously referred to as a string of pearls.

LYMPH NODES 

Lymph nodes kill pathogens and cancer cells. They also  remove debris and excess fluids. © Lymph Notes.com

There are between 600-700 lymph nodes present in the average human body. It is the role of these nodes to filter the lymph before it can be returned to the circulatory system. Although these nodes can increase or decrease in size throughout life, any nodes that has been damaged or destroyed, does not regenerate.

• Afferent lymphatic vessels carry unfiltered lymph into the node. Here waste products, and some of the fluid, are filtered out.
• In another section of the node, lymphocytes, which are specialized white blood cells, kill any pathogens that may be present. This causes the swelling commonly known as swollen glands.
• Lymph nodes also trap and destroy cancer cells to slow the spread of the cancer until they are overwhelmed by it.
• Efferent lymphatic vessels carry the filtered lymph out of the node so that it can continue its return to the circulatory system.

DRAINAGE AREAS

Lymphatic system drainage is organized into two separate, and very unequal drainage areas. The right drainage area clears the right arm and chest. The left drainage area clears all of the other areas of the body including both legs, the lower trunk upper left of the chest, and the left arm.

Lymphatic Drainage Areas © Lymph Notes

WHY THIS INFORMATION 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.
• 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.
• 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 or simplified lympatic drainage, as prescribed by your therapist, is another way in which lymph is encouraged to flow into the capillaries. Each self-massage session begins at the terminus with strokes to stimulate the flow of lymph that is already in the system. This is followed by specialized strokes that encourage the flow of lymph into the capillaries and then upward to the terminus.

© LymphNotes.com 2012. This information does not replace the advice of a qualified health care professional.

A SPECIAL LEARNING BONUS!

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Category: The Lymphatic System Updated: 2012-07-28