The Hematologist is the expert in the diagnosis and treatment of this disorder. The lymphatic system, composed of widely spread and structurally distinct tissues, provides vertebrates, including humans, with immune defenses, filters foreign substances and cell debris from blood and destroys them, and produces lymphocytes, which circulate in blood and lymph vessels. Lymph passes from capillaries to lymph vessels and flows through lymph nodes that are located along the course of these vessels. Cells of the lymph nodes phagocytize, or ingest, such impurities as bacteria, old red blood cells, and toxic and cellular waste. Finally, lymph flows into the thoracic duct, a large vessel that runs parallel to the spinal column, or into the right lymphatic duct, both of which transport the lymph back into veins of the shoulder areas.
All lymph vessels contain one-way valves to prevent backflow.
Tissues of the lymphatic system include the spleen, thymus, bone marrow, and aggregates of lymphatic tissue located in the intestines, tonsils, and adenoids. The spleen, thymus, and bone marrow manufacture lymphocytes, which are the major cell type of the system. The spleen also is involved with destruction of old cells and other substances by phagocytosis, and plays a role in immune responses. The thymus, in humans, is considered the central organ that controls lymphocyte production and antibody formation. Lymph fluid from lacteals is milky white because of the fat globules that are present.