Lymph system; drawing shows the lymph vessels and lymph organs including the lymph nodes, tonsils, thymus, spleen, and bone marrow. One inset shows the inside structure of a lymph node and the attached lymph vessels with arrows showing how the lymph (clear fluid) moves into and out of the lymph node. Another inset shows a close up of bone marrow with blood cells.

Anatomy of the lymph system, showing the lymph vessels and lymph organs including lymph nodes, tonsils, thymus, spleen, and bone marrow. Lymph (clear fluid) and lymphocytes travel through the lymph vessels and into the lymph nodes where the lymphocytes destroy harmful substances. The lymph enters the blood through a large vein near the heart.