So within our entire cardiovascular system our Q remains constant. Q is simply the flow of blood within our system. The flow of blood doesn't actually change because we have a closed cardiovascular circuit, a closed cardiovascular system. Now, what does change within the blood vessels is the A the cross sectional area and B the velocity of that fluid. Now, it turns out that if we take the sum of all the cross sectional areas of all the individual capillaries it will be much greater than the cross sectional area of the arteries and of the veins. So that cross sectional area, the total cross sectional area for the capillaries is the greatest.