Lymph is tissue fluid that flows between cells in all bodily tissues and is transported away by lymphatic vessels. It contains metabolites (e.g. remnants of dead cells and proteins). In the lymphatic vessels, muscle cells may be found, which transport the lymph in the direction of the abdomen and the chest (“lymph pump”). These muscle cells can’t drain the tissue fluid on their own, therefore they rely on the pumping system of the musculature.