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GCSE Biology · GCSEChapter 6 · The heart, blood and circulation
GCSE · Chapter 6

The heart, blood and circulation

By the end of this chapter you will be able to

  • Label a heart and trace blood through the two circuits
  • Compare arteries, veins and capillaries, and explain their structures
  • Name the components of blood and say what each does
  • Interpret data on risk factors for coronary heart disease
  • Describe how valves, pacemakers and transplants help the heart

You should already know

  • Oxygen, carbon dioxide and aerobic respiration (Chapter 10 links back to this)
  • Diffusion and exchange surfaces (Chapter 3)

Where this leads

  • Lungs and gas exchange (Chapter 7)
  • Immunity and white blood cells (Chapter 13)
  • Hormones and the heart rate (Chapter 12)

GCSE Biology. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Describe the heart as a double pump, with pulmonary and systemic circuits, Compare the structure and function of arteries, veins and capillaries, Describe the components of blood and their functions, Explain coronary heart disease, its risk factors, and treatments such as statins, stents and bypass surgery, Describe heart valves, artificial pacemakers and heart transplants.

Exercise P  Do you remember?

1
FWhat is 3 multiplied by 4 multiplied by 5? Write the number.
2
FWhich organelle releases energy in a cell? Write the word.
3
FWhich gas do cells need for aerobic respiration? Write the word.
4
FWhich substance carries oxygen in the blood? Write the word.
5
FWhat is 25 percent of 200? Write the number.
6.1

The heart and double circulation

GCSE
Describe the heart as a double pump, with the pulmonary and systemic circuits, Label the parts of the heart
Video lesson: The heart and double circulationComing soon
Context. Ali is sprinting for the bus. His heart beats faster, and his breathing speeds up. “Why does my heart need to work harder?” he asks. To understand this, we need to follow the blood round the body.

The heart is two pumps in one. The right side pumps deoxygenated blood to the lungs through the pulmonary artery. Blood returns from the lungs to the left side through the pulmonary vein. The left side then pumps oxygenated blood round the rest of the body through the aorta. The body’s blood returns to the right side through the vena cava.

The heart has four chambers. The atria receive blood, and the ventricles pump blood out. The walls of the left ventricle are thicker than those of the right ventricle, because it pumps blood round the whole body at a higher pressure.

right atriumleft atriumright ventricleleft ventriclethicker wall
Simplified heart with the four chambers, and the thicker left ventricle wall
hearttwo pumps in one organlungsbodypulmonary circuit: heart to lungs and back (blue = deoxygenated, red = oxygenated)
The two circuits: pulmonary and systemic (body)

Key ideas

  • The right side of the heart pumps blood to the lungs.
  • The left side pumps oxygenated blood to the whole body.
  • The left ventricle has the thickest muscle wall.
  • The blood goes through the heart twice on each circuit of the body.
Worked example 6.1.1
Name the blood vessel that carries blood from the heart to the lungs. Write the words.

Method. Recall the vessel from the right side of the heart.

  1. Recall. The right ventricle pumps blood to the lungs in the pulmonary artery.
    pulmonary artery
  2. Name it. So the vessel is the pulmonary artery.
    pulmonary artery
  3. Write the answer.
    pulmonary artery

Check. The pulmonary artery carries deoxygenated blood. ✓

Worked example 6.1.2
Name the chamber that receives oxygenated blood from the lungs. Write the words.

Method. Recall where the lungs send blood.

  1. Recall. Blood from the lungs returns through the pulmonary vein.
    pulmonary vein
  2. Name it. It enters the left atrium.
    left atrium
  3. Write the answer.
    left atrium

Check. The left atrium receives oxygenated blood. ✓

Worked example 6.1.3
Explain why the left ventricle wall is thicker than the right ventricle wall. Write one sentence.

Method. Think about where each side pumps blood.

  1. Think. The left ventricle pumps blood round the whole body.
    whole body
  2. Conclude. It needs more force, so its muscle wall is thicker.
    more force
  3. Write the answer.
    The left ventricle pumps blood to the whole body, so it needs a thicker muscle wall for more force.

Check. The right ventricle only pumps to the nearby lungs. ✓

Watch out

Watch out: the pulmonary artery carries deoxygenated blood, although it is an artery. Arteries are defined by carrying blood away from the heart.

Exam tip

Exam tip. When you trace blood, say where it comes from and where it goes. “Lungs to left atrium” is clearer than “to the heart”.

Try it (with your teacher). With your teacher, look at a model or a labelled picture of the heart. Trace the path of blood from the body to the lungs and back, naming each chamber and vessel.

Exercise 6A  The heart and double circulation

1
FName the chamber of the heart that receives blood from the body. Write the words.
2
FName the vessel that carries blood from the heart to the body. Write the word.
3
FName the vessel that carries oxygenated blood from the lungs to the heart. Write the words.
4
FName the vessel that carries deoxygenated blood to the lungs. Write the words.
5
FWhich side of the heart pumps blood to the lungs: the left or the right? Write the word.
6
FWhich chambers of the heart are the atria? Write the words.
7
FWhich chambers pump blood out of the heart? Write the words.
8
FIs the blood in the pulmonary vein oxygenated? Write yes or no.
9
FName the circuit that carries blood between the heart and the lungs. Write the word.
10
FName the circuit that carries blood between the heart and the rest of the body. Write the word.
11
PSWhy is the heart described as a double pump? Write one sentence. Accept any sentence that says it pumps blood through two circuits, one to the lungs and one to the body.
12
PSAli’s heart beats faster when he sprints. Explain why this is useful for his muscles, in one sentence. Accept any sentence that says faster beats deliver more oxygen and glucose to the muscles.
13
PSThe heart beats 70 times per minute at rest. Calculate the number of beats in one hour. Write the number.
14
RChallenge: explain why blood must pass through the lungs before returning to the left side of the heart. Write two sentences. Accept any answer that says the blood picks up oxygen in the lungs, so the left side can pump oxygenated blood to the body.
6.2

Arteries, veins and capillaries

GCSE
Compare the structure and function of arteries, veins and capillaries, Explain how each vessel is adapted
Video lesson: Arteries, veins and capillariesComing soon
Context. Priya compares two tubes: an artery, which feels firm and springy at the wrist, and a vein, which is thinner and softer. “Why do they feel so different?” she asks. The answer lies in the job each vessel does.

Arteries carry blood away from the heart at high pressure. They have a thick, elastic wall with muscle, and a narrow lumen (the inside). Veins carry blood back to the heart at low pressure. They have thin walls, a wide lumen, and valves that stop the blood flowing backwards. Capillaries are very narrow vessels with walls only one cell thick, where substances are exchanged with the cells.

FeatureArteryVeinCapillary
carries bloodaway from the heartto the heartbetween arteries and veins
wallthick, elastic and muscularthin, with little muscleone cell thick
lumen (inside)narrowwidevery narrow
pressure of bloodhighlowlow
valvesno (except at the heart)yesno
Arteries, veins and capillaries compared

Key ideas

  • Arteries: thick, elastic walls; narrow lumen; high pressure; carry blood away from the heart.
  • Veins: thin walls; wide lumen; valves; low pressure; carry blood to the heart.
  • Capillaries: one cell thick; very narrow; exchange with the cells.
  • Capillaries have a very large total surface area for exchange.
Worked example 6.2.1
Name the vessel with valves that stop blood flowing backwards. Write the word.

Method. Recall which vessel has valves.

  1. Recall. Veins have valves to prevent the backflow of blood.
    prevent backflow
  2. Name it. So the vessel is a vein.
    vein
  3. Write the answer.
    vein

Check. Arteries have valves only at the heart. ✓

Worked example 6.2.2
Name the vessel with the thickest muscle layer in its wall. Write the word.

Method. Recall the wall structure of each vessel.

  1. Recall. Arteries have a thick wall with a lot of muscle and elastic tissue.
    thick wall
  2. Name it. So the vessel is an artery.
    artery
  3. Write the answer.
    artery

Check. The thick wall copes with the high pressure. ✓

Worked example 6.2.3
Explain why capillary walls are only one cell thick. Write one sentence.

Method. Think about the job of a capillary.

  1. Think. Capillaries exchange substances with the cells.
    exchange substances
  2. Conclude. A thin wall gives a short distance for diffusion.
    short distance
  3. Write the answer.
    A thin wall gives a short distance for substances to diffuse between blood and cells.

Check. Short distance means faster diffusion. ✓

Watch out

Watch out: arteries do not always carry oxygenated blood, and veins do not always carry deoxygenated blood. The pulmonary artery and pulmonary vein are the exceptions.

Exam tip

Exam tip. When you compare vessels, use the words wall, lumen, pressure and valves. Use the same words for each vessel.

Try it (with your teacher). With your teacher, find your pulse at the wrist. Count the beats for 15 seconds, then multiply by 4. Explain why the pulse can be felt in an artery but not in a vein.

Exercise 6B  Arteries, veins and capillaries

1
FWhich vessels carry blood away from the heart? Write the word.
2
FWhich vessels carry blood back to the heart? Write the word.
3
FWhich vessels have the narrowest lumen? Write the word.
4
FWhich vessel has a wide lumen and valves? Write the word.
5
FWhich vessel has the highest blood pressure? Write the word.
6
FWhich vessel has walls that are only one cell thick? Write the word.
7
FName the valves in veins, and say what they prevent. Write the words.
8
FWhich vessel has a thick, elastic wall to cope with high pressure? Write the word.
9
PSWhy do capillaries have a very large total surface area? Write one sentence. Accept any sentence that says there are very many capillaries, so the total surface is large.
10
PSA pupil says all arteries carry oxygenated blood. Write yes or no, and give one reason. Accept any answer that says the pulmonary artery carries deoxygenated blood to the lungs.
11
PSExplain why a vein has valves but an artery does not, in one sentence. Accept any sentence that says blood in veins is at low pressure, so valves are needed to keep it moving towards the heart.
12
RChallenge: explain why capillaries are the best place for exchange, in two sentences. Accept any answer that gives the thin wall and the close contact with cells, plus the large total surface area.
6.3

Blood and its components

GCSE
Describe the components of blood and their functions
Video lesson: Blood and its componentsComing soon
Context. A pupil cuts a finger in science. The bleeding slows, then stops. “Which part of the blood does that?” she asks. Blood is more than one thing: it has a liquid part and three types of cell, and each has a different job.

Blood is made of plasma (a straw-coloured liquid) and three kinds of cell. Red blood cells carry oxygen using haemoglobin, and they have no nucleus. White blood cells defend the body against pathogens. Platelets are small fragments of cells that help the blood clot.

Plasma carries dissolved substances, including glucose, carbon dioxide, urea and hormones, around the body.

ComponentJobNotes
plasmacarries dissolved substances, such as glucose, carbon dioxide, urea and hormonesa straw-coloured liquid
red blood cellscarry oxygen, using haemoglobinno nucleus; biconcave disc shape
white blood cellsfight pathogens (phagocytes engulf them; lymphocytes make antibodies)have a nucleus
plateletshelp the blood clot at a woundsmall cell fragments
The components of blood and their functions

Key ideas

  • Plasma carries dissolved substances around the body.
  • Red blood cells carry oxygen, using haemoglobin, and have no nucleus.
  • White blood cells fight pathogens; phagocytes engulf them and lymphocytes make antibodies.
  • Platelets help the blood clot at a wound.
Worked example 6.3.1
Name the blood component that carries oxygen. Write the word.

Method. Recall the cell that carries oxygen.

  1. Recall. Red blood cells carry oxygen, using haemoglobin.
    carry oxygen
  2. Name it. So the component is red blood cells.
    red blood cells
  3. Write the answer.
    red blood cells

Check. Haemoglobin is inside red blood cells. ✓

Worked example 6.3.2
Name the blood component that helps the blood clot. Write the word.

Method. Recall the clotting fragments.

  1. Recall. Platelets are small cell fragments that help the blood clot.
    help the blood clot
  2. Name it. So the component is platelets.
    platelets
  3. Write the answer.
    platelets

Check. Clotting stops the bleeding. ✓

Worked example 6.3.3
Name one substance carried by the plasma. Write the word.

Method. Recall what plasma carries.

  1. Recall. Plasma carries dissolved substances such as glucose and carbon dioxide.
    dissolved substances
  2. Name one. Glucose is one of them.
    glucose
  3. Write the answer.
    glucose

Check. Other answers include carbon dioxide, urea and hormones. ✓

Watch out

Watch out: red blood cells carry oxygen, but the plasma carries carbon dioxide. Do not say that the red blood cells carry carbon dioxide.

Exam tip

Exam tip. Name the component and then its job. “White blood cells fight pathogens” scores more than “white blood cells” on their own.

Try it (with your teacher). With your teacher, look at a prepared slide or a labelled photograph of human blood. Count the red and white cells in one field of view, and say why there are far more red blood cells.

Exercise 6C  Blood and its components

1
FName the liquid part of the blood. Write the word.
2
FWhich cells carry oxygen? Write the words.
3
FWhat is the name of the protein in red blood cells that carries oxygen? Write the word.
4
FDo red blood cells have a nucleus? Write yes or no.
5
FWhich blood cells fight pathogens? Write the words.
6
FWhich blood cells engulf pathogens? Write the word.
7
FWhich blood cells make antibodies? Write the word.
8
FWhich cell fragments help blood to clot? Write the word.
9
FName the substance in plasma that carries carbon dioxide away from the cells. Write the word. Accept carbon dioxide.
10
PSWhy does a cut stop bleeding? Write one sentence. Accept any sentence that says platelets clot the blood to seal the wound.
11
PSExplain why red blood cells have no nucleus. Write one sentence. Accept any sentence that says the space is used for more haemoglobin, so more oxygen can be carried.
12
PSA pupil counts 500 red blood cells and 5 white blood cells in one field of view. Calculate how many red blood cells there are for each white blood cell. Write the number.
13
RChallenge: explain why the blood is needed to carry both oxygen and carbon dioxide, but using different parts of the blood. Write two sentences. Accept any answer that says red blood cells carry oxygen while plasma carries dissolved carbon dioxide.
6.4

Coronary heart disease and risk factors

GCSE
Explain coronary heart disease and the role of the coronary arteries, Interpret data on risk factors
Video lesson: Coronary heart disease and risk factorsComing soon
Context. Ravi’s uncle has pain in his chest when he walks up hills. His doctor explains that the arteries that supply the heart muscle have become narrow. “Why would arteries become narrow?” Ravi asks. The answer is coronary heart disease.

The coronary arteries supply the heart muscle with oxygen and glucose. In coronary heart disease (CHD), fatty material builds up inside the coronary arteries, narrowing them. Blood flow to the heart muscle is reduced, which can cause chest pain (angina) or a heart attack if a vessel is blocked.

Risk factors increase the chance of developing CHD. They include a diet high in saturated fat and salt, smoking, stress and physical inactivity. A risk factor is linked to the disease but does not always cause it.

Group (invented data)With CHDTotalPercentage with CHD
smokers124030%
non-smokers81605%
Smoking and coronary heart disease (invented data for practice)
CHD in adults by activity (invented data)048121620very activeactiveinactiveactivity levelpercentage with CHD (%)
Percentage of adults with CHD by activity level (invented data)

Key ideas

  • Coronary arteries supply the heart muscle with oxygen and glucose.
  • CHD narrows the coronary arteries with fatty build-up.
  • Risk factors include diet, smoking, stress and inactivity.
  • A risk factor is linked to CHD; it does not always cause it.
Worked example 6.4.1
Work out the percentage of smokers with CHD in the table. Write the number, with the percentage sign.

Method. Divide the number with CHD by the total, then multiply by 100.

  1. Divide. Smokers: 12 / 40 = 0.3.
    12 / 40 = 0.3
  2. Multiply. Multiply by 100 to give a percentage.
    0.3 x 100 = 30
  3. Write the answer.
    30%

Check. 30% of 40 is 12. ✓

Worked example 6.4.2
Compare the chance of CHD for smokers and non-smokers in the table. Write how many times more likely the smokers are, to the nearest whole number.

Method. Divide the smokers’ percentage by the non-smokers’.

  1. Read. Smokers: 30%. Non-smokers: 5%.
    30% and 5%
  2. Divide. Divide 30 by 5 to compare the two.
    30 / 5 = 6
  3. Write the answer.
    6

Check. Six times more likely in this invented data. ✓

Worked example 6.4.3
Name the vessels that supply the heart muscle with oxygen. Write the words.

Method. Recall the vessels supplying the heart.

  1. Recall. The heart muscle is supplied by the coronary arteries.
    coronary arteries
  2. Name them. So the vessels are the coronary arteries.
    coronary arteries
  3. Write the answer.
    coronary arteries

Check. These are branches of the aorta. ✓

Watch out

Watch out: a risk factor is linked to CHD; it is not a guaranteed cause. Some people who smoke never develop CHD, and some who do not smoke do.

Exam tip

Exam tip. When you interpret risk-factor data, compare the percentages and say how big the difference is. Do not claim the factor is the only cause.

Try it (with your teacher). With your teacher, find one piece of evidence about physical activity and heart health in a trusted source. Write one sentence saying what it shows, and check it with your teacher.

Exercise 6D  Coronary heart disease and risk factors

1
FName the arteries that supply the heart muscle with oxygen. Write the words.
2
FWhat builds up inside the coronary arteries in coronary heart disease? Write the words.
3
FName one risk factor for coronary heart disease. Accept any one: smoking, a diet high in saturated fat, stress, or physical inactivity.
4
FIn the table, how many smokers had CHD? Write the number.
5
FIn the table, how many non-smokers were in the group? Write the number.
6
PSCalculate the percentage of non-smokers with CHD. Write the number, with the percentage sign.
7
PSIn the activity bar chart, which group has the highest percentage with CHD? Write the words.
8
PSIn the same chart, what percentage of very active adults had CHD? Write the number, with the percentage sign.
9
PSExplain in one sentence why a risk factor does not prove that a factor causes CHD. Accept any sentence that says the link may be affected by other factors, and a risk factor is an association, not a proof.
10
PSWhy does a narrow coronary artery cause chest pain? Write one sentence. Accept any sentence that says less oxygen reaches the heart muscle, so it works harder in pain.
11
RChallenge: the smokers group had a 30% CHD rate and the non-smokers group had 5%. Explain why this difference does not show that all smokers will get CHD. Write two sentences. Accept any answer that says most smokers in this data did not have CHD, so smoking raises the risk, but does not guarantee it.
6.5

Treatments, valves, pacemakers and transplants

GCSE
Describe heart valves and their function, Describe treatments for CHD, artificial pacemakers and transplants
Video lesson: Treatments, valves, pacemakers and transplantsComing soon
Context. Hana’s grandfather has a stent put into a narrowed coronary artery and takes a daily medicine. “Why not just give him a new heart?” Hana asks. There are several ways to treat the heart, and each suits a different problem.

Heart valves keep blood flowing in one direction. They open and close as the heart pumps, so that blood does not flow back into the chamber it has just left.

Statins are medicines that lower blood cholesterol, which reduces the build-up in the coronary arteries. A stent is a small tube that holds a narrowed artery open. A bypass graft is a vessel that goes around a blocked artery. An artificial pacemaker is an electrical device that regulates the heartbeat. A heart transplant replaces a failing heart with a donor heart.

TreatmentWhat it doesType
statinslower the level of blood cholesterolmedicine
stenta tube that holds a narrowed artery opendevice
bypass grafta new vessel that goes around a blocked arterysurgery
artificial pacemakeran electrical device that regulates the heartbeatdevice
heart transplantreplaces a failing heart with a donor heartsurgery
Treatments for heart problems

Key ideas

  • Valves stop blood flowing backwards in the heart.
  • Statins lower blood cholesterol; stents and bypass grafts keep blood flowing.
  • An artificial pacemaker regulates the heartbeat electrically.
  • A heart transplant replaces a failing heart.
Worked example 6.5.1
Name the treatment that holds a narrowed artery open. Write the word.

Method. Recall the device that is placed in the artery.

  1. Recall. A small tube placed in the artery holds it open; this is a stent.
    holds it open
  2. Name it. So the treatment is a stent.
    stent
  3. Write the answer.
    stent

Check. A bypass graft goes around a blockage instead. ✓

Worked example 6.5.2
Name the medicine that lowers blood cholesterol. Write the word.

Method. Recall the medicine.

  1. Recall. Statins are medicines that lower the level of blood cholesterol.
    lower blood cholesterol
  2. Name it. So the medicine is a statin.
    statin
  3. Write the answer.
    statin

Check. Statins reduce fatty build-up. ✓

Worked example 6.5.3
Explain the job of a heart valve. Write one sentence.

Method. Think about the direction of blood.

  1. Think. Blood must flow in only one direction through the heart.
    one direction
  2. Conclude. Valves open to let blood through, and close to stop it flowing back.
    close to stop it
  3. Write the answer.
    Valves open to let blood through and close to stop it flowing back into the chamber it left.

Check. Valves are in the heart and in veins. ✓

Watch out

Watch out: a stent and a bypass graft are different. A stent holds a narrowed artery open; a bypass graft goes round a blockage.

Exam tip

Exam tip. When you describe a treatment, say what it does, not only its name. “A pacemaker regulates the heartbeat” scores more than “a pacemaker”.

Try it (with your teacher). With your teacher, use a simple model: two balloons joined by a tube, and a clip that opens and closes. Show how a valve allows flow in one direction only. Write one sentence about the model.

Exercise 6E  Treatments, valves, pacemakers and transplants

1
FWhat is the job of a heart valve? Write the words.
2
FName the medicine that lowers the level of blood cholesterol. Write the word.
3
FName the small tube that holds a narrowed artery open. Write the word.
4
FName the surgery in which a vessel goes around a blocked artery. Write the words.
5
FWhat does an artificial pacemaker do? Write the words.
6
FWhat does a heart transplant replace? Write the words.
7
FIs a heart transplant a treatment for a narrowed artery? Write yes or no.
8
PSName the tiny vessels that link the arteries and the veins, where exchange happens. Write the word.
9
PSExplain why an artificial pacemaker is useful for a person whose heart beats too slowly. Write one sentence. Accept any sentence that says it sends electrical signals to make the heart beat at a regular rate.
10
PSWhy might a person with a narrowed artery be given a statin as well as a stent? Write one sentence. Accept any sentence that says the statin lowers cholesterol and slows further build-up, while the stent keeps the artery open now.
11
RChallenge: explain why a heart valve that does not close properly would reduce the efficiency of the heart. Write two sentences. Accept any answer that says blood flows back into the chamber, so less blood is pumped forward with each beat.

Chapter summary

SkillMethod
Double pumpRight side to the lungs; left side to the body; the left ventricle wall is thickest.
ArteriesThick, elastic walls; narrow lumen; high pressure; away from the heart.
VeinsThin walls; wide lumen; valves; low pressure; to the heart.
CapillariesOne cell thick; very narrow; exchange with cells.
BloodPlasma carries dissolved substances; red cells carry oxygen; white cells fight pathogens; platelets clot.
CHDFatty build-up narrows the coronary arteries; risk factors include diet, smoking, stress and inactivity.
TreatmentsStatins lower cholesterol; stents hold arteries open; bypass grafts go round blockages; pacemakers and transplants treat the heart itself.

Can you…?

  • I can label the heart and trace blood through the two circuits
  • I can compare arteries, veins and capillaries
  • I can name the components of blood and their functions
  • I can interpret risk-factor data for coronary heart disease
  • I can describe valves, pacemakers, transplants and the main treatments for CHD

Key terms

atrium
an upper chamber of the heart that receives blood
ventricle
a lower chamber of the heart that pumps blood out
aorta
the main artery that carries blood from the left ventricle to the body
pulmonary artery
the artery that carries deoxygenated blood from the heart to the lungs
pulmonary vein
the vein that carries oxygenated blood from the lungs to the heart
capillary
a very narrow vessel with walls one cell thick, where exchange happens
plasma
the straw-coloured liquid part of the blood
haemoglobin
the protein in red blood cells that carries oxygen
platelet
a small cell fragment that helps blood to clot
coronary heart disease
narrowing of the coronary arteries by fatty build-up
statin
a medicine that lowers the level of blood cholesterol
stent
a small tube that holds a narrowed artery open

Exercise 6Z  Check-up

1
Name the vessel that carries blood from the heart to the body. Write the word.
2
Name the vessel that carries deoxygenated blood to the lungs. Write the words.
3
Which chamber has the thickest wall? Write the words.
4
Which vessels have valves and a wide lumen? Write the word.
5
Name the cells that carry oxygen. Write the words.
6
Which blood component helps blood to clot? Write the word.
7
Name the coronary vessels that supply the heart muscle. Write the words.
8
A group of 50 people has 10 with CHD. Find the percentage with CHD. Write the number, with the percentage sign.
9
Name the treatment that goes round a blocked artery. Write the words.
10
Explain in one sentence why veins have valves. Accept any sentence that says the blood in veins is at low pressure, so valves prevent it flowing backwards.

Total 24 marks. Allow about 24 minutes.

Exercise 6X  Exam-style questions

1
FName the vessel that carries blood from the lungs to the left atrium. Write the words.[1 mark]
2
FName the blood component that fights pathogens and engulfs them. Write the word.[1 mark]
3
FName the treatment that lowers the level of blood cholesterol. Write the word.[1 mark]
4
FCompare an artery and a vein, using two differences in structure. Accept any two of: thick, elastic wall in artery; valves in vein; narrow lumen in artery; wide lumen in vein.[2 marks]
5
FDescribe the job of a red blood cell, and say why it has no nucleus. Write two sentences. Accept any answer that says red blood cells carry oxygen using haemoglobin, and the space left by the nucleus holds more haemoglobin.[2 marks]
6
RExplain why the left ventricle wall is thicker than the right ventricle wall. Write two sentences. Accept any answer that says the left ventricle pumps to the whole body at high pressure, while the right ventricle only pumps to the lungs.[3 marks]
7
PSIn the invented data, the percentage of smokers with CHD is 30% and of non-smokers is 5%. Work out how many times greater the percentage is for smokers. Write the number.[2 marks]
8
FDescribe how coronary heart disease develops and how it causes chest pain. Write three points. Accept any three of: fatty material builds up in coronary arteries; arteries narrow; less blood and oxygen reach the heart muscle; this causes pain.[3 marks]
9
FExplain the role of a stent and a bypass graft in treating a narrowed coronary artery. Write two sentences. Accept any answer that says a stent holds the artery open, and a bypass graft goes round the blockage.[4 marks]
10
RA student says a heart valve helps the heart by pumping blood. Explain why this is not quite correct, and describe what a valve does, in three sentences. Accept any answer that says the valve controls direction of flow, opening to let blood through and closing to stop it flowing back, rather than pumping.[5 marks]
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