1.1.2 Structure and function of blood vessels Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 1

The 20 questions

1. Which blood vessel has a single-cell-thick wall that makes it suitable for exchange of materials with tissues?

   • Artery, whose thick elastic wall is one cell thick and carries blood at high pressure
   • Vein, whose wall is thin and contains valves that stop the blood flowing back
   • Capillary, whose endothelium is only one cell thick
   • Arteriole, whose wall is thick and muscular and has a large lumen compared with its wall

2. What is the main function of the elastic tissue in the walls of large arteries?

   • It contracts actively to push blood forward through the artery towards the capillaries
   • It stretches as blood is pumped in and recoils to maintain pressure between heartbeats
   • It stores glucose so that the artery wall can respire anaerobically during exercise
   • It acts as a valve that stops blood flowing back into the heart during ventricular systole

3. Which statement describes the lumen of a vein compared with an artery of similar size?

   • The vein has a narrower lumen and thicker wall, and blood in it is at higher pressure
   • The vein has a wider lumen and thinner wall, and blood in it is at lower pressure
   • The vein has a wider lumen but a thicker wall, and blood in it is at higher pressure
   • The vein has a narrower lumen and thinner wall, and blood in it is at higher pressure

4. Why do veins contain valves while most arteries do not?

   • Veins carry deoxygenated blood, which needs valves to be oxygenated in the lungs
   • Valves in veins pump blood through the capillaries, which arteries cannot do by themselves
   • Blood in arteries flows in one direction only, so valves would be damaged by the high pressure
   • Blood in veins is at low pressure and flows back easily, so valves prevent backflow

5. What is the role of the narrow arterioles in controlling blood flow?

   • They contain valves that open only when the heart is in diastole to let blood reach the lungs
   • They act as the main site of gas exchange because their walls are only one cell thick
   • Their muscular walls can constrict or dilate, changing the flow of blood into capillary beds
   • They carry blood at the highest pressure in the body and so drive blood into the veins

6. Which vessel carries blood at the lowest velocity, and why?

   • Pulmonary artery, because it carries deoxygenated blood that is less viscous and moves slowly
   • Vena cava, because it has the thinnest wall and so blood travels slowly through it
   • Aorta, because it is the widest vessel and blood must slow down at its wall
   • Capillaries, because their total cross-sectional area is very large, so the flow slows

7. A blood pressure reading in a large artery shows the systolic pressure is 120 mmHg and the diastolic pressure is 80 mmHg. What is the pulse pressure?

   • 40 mmHg
   • 20 mmHg
   • 200 mmHg
   • 100 mmHg

8. A capillary is 8 micrometres in diameter and a student models blood flowing through 10 000 such capillaries in parallel. Which factor most determines the rate of exchange at the capillary bed?

   • The number of red blood cells per millilitre, which controls how much oxygen can diffuse out
   • The large total surface area of many capillaries in parallel and the short diffusion distance
   • The valves present at the start of each capillary, which control the rate of blood flow inwards
   • The narrow diameter of a single capillary, which means blood must be pumped through at high pressure

9. Why does the lumen of an artery stay open even when the heart is in diastole?

   • Contraction of smooth muscle in the artery wall pumps blood continuously through the lumen
   • Elastic recoil of the artery wall maintains pressure and keeps blood moving forward
   • The blood in the artery is under gravity pressure only, which keeps the lumen fully open
   • Valves at the entrance to the artery hold the lumen open between heartbeats

10. Which of these is a feature of arteries rather than veins?

    • A large lumen relative to wall thickness so that blood can return to the heart at low pressure
    • A thin wall with no muscle, so that the vessel can be squeezed by skeletal muscle to move blood
    • A thick muscular and elastic wall that withstands the high pressure of blood pumped from the heart
    • Valves along the length of the vessel that prevent blood flowing backwards under gravity

11. Why is the wall of the aorta thicker than that of the pulmonary artery?

    • The aorta carries deoxygenated blood, which needs a thicker wall to limit diffusion of oxygen out
    • The aorta is the first vessel to receive blood from the capillaries, so it must be thicker
    • The pulmonary artery has valves that take the place of thick muscle in its wall
    • The aorta carries blood at a higher pressure round the whole body than the pulmonary artery does to the lungs

12. Which change would most reduce the velocity of blood as it flows from arteries into capillaries?

    • A decrease in the total cross-sectional area as the arteries narrow into arterioles
    • A huge increase in total cross-sectional area as the vessels branch into many capillaries
    • An increase in the number of valves along the capillary walls to stop blood flowing backwards
    • A rise in blood pressure as the blood moves from the arteries into the capillaries

13. Why does a capillary wall need to be permeable to small molecules such as glucose and oxygen?

    • So that blood plasma can be pumped by the heart through the walls to reach the veins
    • So that large proteins can move out of the blood and form the valves in the veins
    • So that these substances can diffuse out of the blood into the tissue fluid around the cells
    • So that red blood cells can move out of the capillary and enter the tissue to deliver oxygen

14. Which description best matches a vein's structure in relation to its function?

    • Thick elastic walls and narrow lumen allow blood to be propelled at high pressure to the capillaries
    • One cell thick walls allow rapid exchange of gases and nutrients with the surrounding tissue
    • Muscular walls control the diameter of the vessel so that blood flow into capillaries is regulated
    • Thin walls and large lumen reduce resistance so blood returns to the heart, aided by valves and skeletal muscle squeeze

15. Blood in a capillary bed moves slowly. Which is the best explanation of why this matters for exchange?

    • Slow flow stops the blood clotting in the capillaries, which keeps the exchange surface clear
    • Slow flow raises the pressure in the capillaries, which forces gases through the capillary walls
    • Slow flow gives more time for substances to diffuse between the blood and the tissue fluid
    • Slow flow means the red blood cells are able to pass through the walls of the capillaries more easily

16. A student measures the wall thickness of an artery as 1.0 mm and the internal diameter of its lumen as 4.0 mm. What is the ratio of wall thickness to lumen diameter?

    • 1:4
    • 4:1
    • 1:1
    • 1:2

17. Which feature of arterioles allows them to alter the distribution of blood to different tissues?

    • Valves in their walls that open and close in response to the heartbeat
    • Thin endothelium that allows blood to pass directly into the tissue without a wall
    • Smooth muscle in their walls that can contract or relax to change the diameter of the vessel
    • Elastic tissue that stretches only during diastole to control the flow of blood

18. Why does exercise cause arterioles supplying skeletal muscle to dilate?

    • The muscle cells need less blood so that the heart can rest and the muscle can contract more forcefully
    • The pressure in the arterioles must fall so that blood can be pumped back up to the heart
    • The arterioles need to stop blood entering the muscle so that lactic acid can be removed more quickly
    • The muscle needs more oxygen and glucose delivered to it, so more blood is directed to the muscle

19. Why does blood pressure fall as blood moves from the arteries through the arterioles to the capillaries?

    • Veins take blood from the capillaries at the highest pressure, so pressure falls only at the heart itself
    • Blood is pumped more slowly in the capillaries, so the heart's pressure gradient is reversed in each vessel
    • Arterioles contain valves that open and close, which allows blood pressure to fall in steps along the route
    • Resistance to flow is high in the narrow arterioles, and energy is lost to friction as blood moves through the vessels

20. A student measures the blood flow velocity in the aorta as 30 cm/s and the cross-sectional area of the aorta as 4.0 cm^2. What is the volume flow rate?

    • 0.13 cm^3/s
    • 7.5 cm^3/s
    • 120 cm^3/s
    • 34 cm^3/s

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