The human double circulation has both : a circulation taking blood to and from the body tissues, and a circulation taking blood to and from the tissues of the lungs. The graph shows the change in mean blood pressure in the blood vessels as blood passes to and from the body tissues. [Figure 4 (Line graph showing mean blood pressure / arbitrary units on the y-axis, from 0 to top, against blood vessels on the x-axis, labelled arteries, capillaries, veins. The line starts high in arteries, drops sharply in capillaries, and continues to drop to a low level in veins.)]

1. (a)(i)Name, for the circulation shown in the graph the first artery that blood enters with the highest mean blood pressure[1]
2. (a)(ii)the last vein that blood enters with the lowest mean blood pressure.[1]
3. (b)Explain, using your knowledge of the structures of arteries and veins, the change in mean blood pressure shown in the graph.[3]
4. (c)Describe, with reference to the movement of named substances, the process that takes place as blood passes through the capillaries of the body tissues.[3]
5. (d)Draw on the graph on page 8 a line to show the change in the mean blood pressure as blood passes to and from the tissues of the lungs.[2]

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