Lymphatic system structure. (a) The lymphatic system is separated into two distinct sets of tubules. Lymphatic vessels drain various areas of the body passing the material through a series of lymph nodes before returning the material to the venous circulation through the thoracic ducts. (b) Lymphatic capillaries drain interstitial fluid that accumulates during capillary exchange. The protein and cell-rich fluid termed lymph is then transported into vein-like valved collecting tubules. (c) Anchoring filaments couple lymphatic capillary endothelial cells to the surrounding matrix. Forces applied through these anchoring filaments enhance lymphatic permeability to promote tissue drainage.