The formation of lymph occurs when the balance of Starling’s forces causes fluid to filter into the interstitium. This fluid is reabsorbed at the venous side, with the remaining fluid becoming interstitial fluid and flowing into lymphatic vessels to be cleared.
The flow of lymph is facilitated by the endothelial cells of the lymphatic capillary, which are attached by anchoring filaments. The edges of the cells overlap, forming a minute valve. When interstitial fluid pressure is raised, the valve can open and fluid can flow directly into the lymphatic capillary. The accumulation of lymph in the capillary prevents the flap from opening.
Overall, the composition of lymph is greatly influenced by the tissue from which it is formed. The electrolytes and water content of lymph is similar to the extracellular fluid (ECF) and it contains cell debris and products of tissue metabolism.
Factors affecting formation of lymph: