Interstitial Fluid Collection Flow
a, Interstitial fluid, collected by the initial lymphatic capillary plexus, is transported by pre-collector lymphatic vessels to larger collecting lymphatic vessels and returned to the circulation through the thoracic duct. Collecting lymphatic vessels have smooth muscle cell coverage (red) and luminal valves to propel and maintain unidirectional lymph flow. Deep lymphatic vessels run along arteries and veins. b, Schematic cross-section of skin, showing the relative positions of blood and lymphatic vessels. c, Mechanism of interstitial tissue fluid uptake by a lymphatic capillary. Plasma components, extravasated white blood cells and particulate matter, such as bacteria, enter the lymphatic vessels through loose valve-like openings. Lymphatic vessels are linked to the extracellular matrix by anchoring filaments. The latter are very thin (4–10 nm) fibrillin-containing filaments, which are inserted into the endothelial cell plasma membrane. Anchoring filaments prevent vessel collapse in conditions of high interstitial pressure.