Organization of lymphatic vasculature. (A) The lymphatic vasculature resorbs fluid, macromolecules, and cells from the interstitium. (B) Mechanism of lymph formation in capillaries. Interstitial components penetrate lymphatic capillaries via openings between LECs. The specialized structure of such openings prevents the return of lymph back to the interstitium. Anchoring filaments attach LECs to the ECM and prevent vessel collapse under conditions of increased interstitial pressure (black arrow). (C) Junctional organization of LECs in lymphatic capillaries and collecting vessels. Both “buttons” and “zippers” share a repertoire of adherens and tight junction–associated proteins (e.g., VE-cadherin, zonula occludens-1, occludin, and claudin-5). The main difference between them resides in their organization (Baluk et al., 2007). (D) Mechanism of lymph propulsion in collecting vessels. Coordinated opening and closure of lymphatic valves is important for efficient lymph transport. SMCs covering each lymphangion possess intrinsic contractile activity. EC, endothelial cell.