Figure 1. Lymph transport along lymphatic vessels. (A) Unidirectional lymph flow route: lymphatic capillaries collect peripheral tissue fluid and converge into larger collecting vessels, then lymph drains into the lymph node from the afferent lymphatic vessels and flows out from the efferent lymphatic vessel. Afterwards lymph fluid flows through the thoracic duct and the right lymphatic trunk, eventually enters into venous circulation. Arrows indicate the direction of lymph flow. (B) Interstitial fluid, macromolecules and immune cells which extravasate from blood vessels are collected by lymphatic capillaries. Initial lymphatics are composed of a layer of oak leaf-shaped endothelial cells and lack of muscle layers. (C) Lymphatic collectors contain intraluminal valve and SMC layers that enable the unidirectional lymph flow.