Circulatory system vs the lymphatic system
The lymph-vascular system collects, transports and filters "waste products" such as protein, foreign bodies, metabolic waste or inflammation products released into tissue fluid.
In contrast to the circulatory system that together with the heart forms a closed circuit, the lymphatic system is a semi-open system of vessels. Lymph liquid flows in the latter, also referred to as lymph. This liquid is an albuminous bodily fluid - in the case of abrasion recognizable as discharge on the skin´s surface. This liquid flows in its own vascular system, the lymphatic system, which works parallel to the body´s venous system. Whereas blood circulation is kept going by the heart, the lymphatic system does not have such a motor.
However, there is no need, as the lymphatic pathways do not form a closed circuit but begin in the interstitial tissue. Lymph is mainly transported through the activity of the lympathic vessels.
Structure and function
Parallel to the venous system the lymphatic system covers the whole body like a network. The lymph drainage system consists of lymph capillaries, lymph collectors, lymph nodes and lymphatic trunks. Unlike the closed venous and arterial system, it functions, however, as a one way street: the lymphatic system accumulates, transports and filters "waste", such as protein, debris or metabolic waste released into the tissue fluid.
Lymphatic vessels absorb from the interstitial tissue the protein dissolved into water. Enriched with fats, cellular waste, debris and bacteria the lymph fluid transports the protein bodies via larger lymphatic vessels back into the venous system - up to 2 litres per day. The lymphatic system is thus connected with the circulatory system. Lymphatic vessels have the diameter of a hair, at the most that of an uncooked spaghetti.