(a)[2]
Explain the meaning of a closed double circulation.
(b)[2]
Table 1.1 presents some structures in the mammalian circulatory system. Complete Table 1.1 to show the order of the structures through which blood flows, beginning with the pulmonary vein. Use the numbers $2$ to $5$ to show the correct sequence.
(c(i))[2]
Explain why the walls of arteries are thicker than those of veins.
(c(ii))[4]
Smoking allows carbon monoxide and nicotine to enter the blood. Describe the short-term effects of each of these substances on the cardiovascular system.