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Lymphatic Disease

The lymphatic system clears away infection and keeps your body fluids in balance. If it's not working properly, fluid builds in your tissues and causes swelling, called lymphedema. Other lymphatic system problems can include infections, blockage, and cancer.

Like the venous system, the lymphatic system transports fluids throughout the body. The lymphatic system consists of thin-walled lymphatic vessels, lymph nodes, and two collecting ducts (see Lymphatic System: Helping Defend Against Infection). Lymphatic vessels, located throughout the body, are larger than capillaries, and most are smaller than the smallest veins. Most of the lymphatic vessels have valves like those in veins to keep the lymph, which can clot, flowing in the one direction. Lymphatic vessels drain fluids that have diffused through the very thin walls of capillaries. The fluids contain proteins, minerals, nutrients, and other substances, which provide nourishment to tissues. However, most of the fluid is reabsorbed into the capillaries. The rest of the fluid (lymph) is drained from the spaces surrounding the cells into the lymphatic vessels, which eventually return it to the veins. Lymphatic vessels also collect and transport damaged cells, cancer cells, and foreign particles (such as bacteria and viruses) that may have entered the tissue fluids.

All of lymph passes through strategically placed lymph nodes, which filter damaged cells, cancer cells, and foreign particles out of the lymph. Lymph nodes also produce specialized blood cells designed to engulf and destroy damaged cells, cancer cells, and foreign particles. Thus, important functions of the lymphatic system are to remove damaged cells from the body and to provide protection against the spread of infection and cancer.

The lymph vessels drain into collecting ducts, which empty their contents into the two subclavian veins, located under the collarbones. These veins join to form the superior vena cava, the large vein that drains blood from the upper body into the heart.

The lymphatic system is a vital part of the immune system, along with the thymus gland, bone marrow, spleen, tonsils, liver, appendix, and Peyer's patches in the small intestine.

The lymphatic system is a network of lymph nodes connected by lymphatic vessels. This system transports lymph. Fluids that contain oxygen, proteins, and other nutrients seep through the thin walls of capillaries into the body's tissues to nourish them. Some of these fluids enter the lymphatic vessels to be returned eventually to the bloodstream. The fluids also transport foreign substances (such as bacteria), cancer cells, and dead or damaged cells that may be present in tissues into the lymphatic vessels. Lymph also contains many white blood cells.

All substances transported by the lymph pass through at least one lymph node, where foreign substances can be filtered out and destroyed before fluids are returned to the bloodstream. In the lymph nodes, white blood cells can collect, interact with each other and antigens, and generate immune responses to foreign substances. Lymph nodes contain a mesh of tissue in which lymphocytes are tightly packed. Harmful microorganisms are filtered through the mesh, then attacked by lymphocytes and macrophages (which are also present in the lymph nodes). Lymph nodes are often clustered in areas where the lymphatic vessels branch off, such as the neck, armpits, and groin.

The secondary lymphoid organs include the spleen, lymph nodes, tonsils, liver, appendix, and Peyer's patches in the small intestine. These organs trap microorganisms and other foreign substances and provide a place for mature cells of the immune system to collect, interact with each other and with the foreign substances, and generate a specific immune response.

The lymph nodes are strategically placed in the body and are connected by an extensive network of lymphatic vessels, which act as the immune system's circulatory system. The lymphatic system transports microorganisms, other foreign substances, cancer cells, and dead or damaged cells from the tissues to the lymph nodes and then to the bloodstream. Lymph nodes are one of the first places that cancer cells can spread. Thus, doctors often evaluate lymph nodes to determine whether a cancer has spread. Cancer cells in a lymph node can cause the node to swell. Lymph nodes can also swell after an infection, because immune responses to infections are generated in lymph nodes.