Human Body Resource & Guide

Lymphatic System

The lymphatic system is an open-ended system for returning interstitial fluid from the peripheral tissues to the heart. It is a one-way system that travels through the lymph nodes and carries lymphatic fluid which contains only a few cells, mostly lymphocytes. Interstitial fluid is generated when fluid is passed from capillaries into the interstitial space (approximately 10% of capillary blood flow). It is important that this fluid and protein be returned to the main circulation. The system is one way because of one-way valves present within the lymphatic vessels that permit flow in only one direction. The lymphatic vessels are extremely small and thin and do not contain smooth muscle in their walls. Fluid is moved along mostly by the compression of surrounding skeletal muscles and tissues, though some intrinsic contraction may occur.

The lymphatic system is also important in fighting infection and cancer spread. The lymph fluid percolating through the lymph nodes carries with it any molecules the body considers foreign (called antigens) including bacteria, viruses and cancer cells. When these infectious or cancer molecules reach the lymph nodes, they stimulate certain cells (called B cells) to produce antibodies which attach themselves to the antigens on the surface of the foreign cells. The antibodies initiate a chemical response of the complement system which damages or kills the foreign cells and signals other components of the immune system. The antibodies travel throughout the body to fight the infection wherever it is encountered. Other organs involved in the production of antibodies and other aspects of the immune system include the thymus, spleen, bone marrow, tonsils and lymphoid follicles of the digestive system.

The lymphatic system also aids digestion by transporting fat absorbed in the gastrointestinal system to the blood stream via lacteals. Without this, malnutrition would develop.

Diseases of the lymphatic system include lymphedema, its role in the immune system and autoimmune diseases, congenital deficiencies and certain types of cancer (lymphoma). Filariasis is a significant health problem in certain parts of the world including Africa, India and south Asia, affecting 100 million people world-wide. It is transmitted human to human by certain species of mosquitoes. The nematodes lodge in the lymphatics and block normal flow producing great enlargement of arms, legs, genetalia and others (elephantiasis). Damage to the lymphatic system and lymphedema can also result from trauma, congenital deficiency, surgery and radiation.

Diseases of the lymphatic system include:

• Lymphedema, its role in the immune system and autoimmune diseases
• Congenital Deficiencies
• Certain Types of Cancer (Lymphoma)
• Filariasis is a significant health problem in certain parts of the world including Africa, India and south Asia, affecting 100 million people world-wide. It is transmitted human to human by certain species of mosquitoes. The nematodes lodge in the lymphatics and block normal flow producing great enlargement of arms, legs, genetalia and others (elephantiasis).
• Damage to the lymphatic system and lymphedema can also result from trauma, congenital deficiency, surgery and radiation