Lümfisooned

Lümfisooned (lymphatic vessels) form a network of thin-walled channels that transport lymph toward the venous circulation. They collect interstitial fluid that has not been reabsorbed by capillaries and proteins, as well as immune cells such as lymphocytes and antigen-presenting cells. Beginning as microscopic lymphatic capillaries, these vessels coalesce into larger collecting lymphatics, which run alongside the arterial and venous systems. Collecting vessels possess one-way valves and often rely on surrounding smooth muscle to rhythmically contract, assisted by skeletal muscle activity and the respiratory pump to propel lymph.

Throughout the chain, lymph passes through regional lymph nodes, where immune cells sample antigens. Ultimately, lymph drains into lymphatic trunks and ducts, notably the thoracic duct and the right lymphatic duct, which empty into the venous system at the junction of the internal jugular and subclavian veins.

Functions include maintaining interstitial fluid balance, facilitating immune surveillance, and lipid absorption in the gut via specialized lacteals within villi.

Clinical relevance: impairment can lead to lymphedema. Lymphedema can be primary (congenital) or secondary to infection, cancer treatment, or trauma. Lymphatics are routes for metastatic spread of some cancers. Diagnostic imaging includes lymphoscintigraphy and near-infrared fluorescence imaging.

Terminology: lümfisooned refers specifically to the vessels; the lymphatic system also includes lymph nodes, lymphatic ducts, and surrounding tissues.