Blood clots. A blood vessel might be blocked by an embolus. This can be a small mass of debris that moves through the bloodstream. Or it may be blocked by a thrombus. This is a blood clot. Respiratory system. As blood flows in the capillaries during the lungs, carbon dioxide is taken https://www.sgvascularctr.com/a-comprehensive-approach-to-lymphoedema-treatment-a-vascular-surgeons-perspective/