Clinical meaning
The lymphatic system is an extensive network of vessels, nodes, and organs that serves three critical functions: immune surveillance and defense, fluid balance maintenance, and absorption of dietary fats. Unlike the cardiovascular system, the lymphatic system is a one-way system that collects excess interstitial fluid (lymph) from tissues and returns it to the venous circulation via the thoracic duct (which drains into the left subclavian vein) and the right lymphatic duct (which drains the right arm, right side of head, and right thorax into the right subclavian vein). Lymph nodes are small, bean-shaped structures ranging from 1 to 25 millimeters that are distributed throughout the body, with major clusters in the cervical, axillary, inguinal, mediastinal, and mesenteric regions. Each lymph node contains organized zones of B lymphocytes (in follicles), T lymphocytes (in the paracortex), and macrophages that filter lymph fluid, trap and destroy pathogens, and initiate adaptive immune responses. The spleen, the largest lymphatic organ, filters blood rather than lymph and serves as a reservoir for platelets and a site for removal of old or damaged red blood cells. The...