The human blood system includes arteries and veins, the main difference is in the appearance, function and the consequences of embolism, as follows: 1, appearance and color, arterial blood is bright red, venous blood is slightly dark red. The wall of arterial blood vessels is usually thicker, while the wall of venous blood vessels is thinner; 2, blood oxygen content or function, arterial blood pumped from the heart, its blood oxygen content is higher, can supply oxygen to the body tissues or organs. Venous blood mainly plays a reflux role, blood oxygen content is lower, and tissue waste products, so the color is dark red; 3, the consequences of embolism are different, arterial embolism will cause ischemic necrosis of the limb and dry gangrene, venous embolism will cause tissue stasis necrosis, usually wet gangrene.