Lymphatic System

Abstract The lymphatic system consists of a network of vessels lined with endothelial cells and interconnected lymph nodes which are distributed throughout most of the body. It functions as a tissue drainage system which controls blood volume and extracellular fluid volume and prevents tissue oedema. The lymphatic system collects tissue fluids and cells from most organs and tissues and transports it as lymph via a combination of intrinsic and extrinsic lymphatic pumps, ultimately discharging the lymph into blood. It also has an important biological role in the turnover of macromolecules which make up the extracellular matrix, fat absorption from the gut and immune function. Large numbers of lymphocytes migrate from the bloodstream into tissues and lymph nodes every day and the lymphatic system has the essential role of returning these cells to the blood, integrating the widely dispersed organs and tissues that make up the immune system. Key Concepts The lymphatic system comprises a network of vessels lined by endothelial cells. Lymphatic vessels drain nearly all tissues and organs in the body and interconnect lymph nodes. Lymphatics are essential for returning proteins, fluids and cells to blood, absorbing fat from the gut and are involved in the homeostasis of interstitial macromolecules. The lymphatic system is a key regulator of extracellular fluid volume and is involved in preventing oedema. The lymphatics play a central role in integrating the immune system.