When viewing a picture of the circulatory system, what do the red and blue blood vessels mean?
Red = oxygenated blood
Blue = non - oxygenated blood
Correct me if I'm wrong, but I believe the blue blood vessels are to identify the veins in your circulatory system, carrying non-oxygenated blood back to the heart (because the oxygen has been diffused to the cells by capillaries for cellular respiration).
The red blood vessels represent the arteries, they carry the oxygenated blood (starting from the aorta) to the entire body, the oxygen being diffused by the capillaries as well.
Blood becomes oxygenated thanks to gas exchange ( CO2 and O2) in the lungs.