The Human Body

Lymph Nodes

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Along the course of the lymphatic vessels are situated the lymph nodes, more commonly called the lymph glands. These nodes are bean-shaped organs containing large numbers of leukocytes, embedded in a network of connective tissue. All the lymph being returned along the lymphatics to the bloodstream must pass through several of these nodes, which filter out infectious and toxic material and destroy it. The nodes serve as a center for the production of phagocytes, which engulf bacteria and poisonous substances (see Immune System). During the course of any infection, the nodes become enlarged because of the large number of phagocytes being produced; these nodes are often painful and inflamed. The swollen glands most often observed are located on the neck, in the armpit, and in the groin. Certain malignant tumors tend to “travel” along the lymphatics; surgical removal of all nodes that are suspected of being involved in the spread of such malignancies is an accepted therapeutic procedure.

OTHER ORGANS

In addition to the lymph nodes that occur in the lymphatic vessels, several organs, composed of similar tissue, are included in the lymphatic system. The largest and most important of these organs is the spleen.

Embryologically, the lymphatic vessels arise as outbuddings from several veins, especially from the internal jugular and iliac veins. The buds spread throughout the body and separate from the venous system at many points.