And just like arteries vary in size we also have a range of different size values for our veins. The largest vein is known as our vena cava. We also have the smaller veins. We have the venuels very tiny veins and then we have the capillaries. Now the capillaries are the blood vessels, very tiny blood vessels that connect the arteries to our veins. And in the capillaries this is where we have the exchange of nutrients for the waste products taking place within our organs and within our tissues.