Lymph

About the Lymph

Lymph is the clear to whitish fluid that flows through the lymphatic system. It begins as interstitial fluid, the fluid that leaks from blood capillaries to bathe the cells of the tissues; most of this is reabsorbed, but the remainder enters thin walled lymphatic capillaries and becomes lymph. It contains water, proteins, salts, cellular debris, and white blood cells, particularly lymphocytes. Lymph is moved by contraction of the vessel walls and surrounding muscles, with valves preventing backflow, and passes through lymph nodes where it is filtered before eventually returning to the blood through the thoracic duct and right lymphatic duct, which drain into the large veins near the neck. Lymph from the intestine, called chyle, appears milky because it carries absorbed dietary fats packaged in chylomicrons. When lymphatic drainage is impaired, for example after removal of lymph nodes during cancer surgery or in parasitic infections such as lymphatic filariasis, fluid accumulates in the tissues, a condition called lymphedema.