• Our blood always flows in a single direction closed circuit.
• It is driven by the heart, and then is transported in blood vessels: arteries and veins.
• Arteries start from the heart and bring oxygen-rich blood and nutrients to all of our organs
• The organs use oxygen and release carbon dioxide
• The veins are then used to bring the blood loaded with carbon dioxide to the heart
• From the heart, the blood goes into the lungs, in which it leaves the carbon dioxide and go on the heart, full of oxygen.
• Then the blood starts again the same circuit... 100,000 times a day!
• From the heart comes the largest artery out, the aorta.
• It is then divides into arteries, which in turn are divided into finer arterioles until reaching capillaries.
• Blood pressure, very strong coming out of the heart, gradually decreases.

How does the blood then reach the heart?

When coming out of the organs, blood passes through the small blood venules and veins and finally through the large vena cava. This is called venous return.