Cambridge IGCSE0610

Circulatory systems

Biology 0610 Chapter Notes

What this chapter covers

Circulatory systemsHeartBlood vesselsBlood

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Circulatory systems notes

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1. The circulatory system

The circulatory system is a system of blood vessels with a pump and valves to ensure one-way flow of blood.

The pump is the heart. The valves prevent blood flowing backwards, so it moves in one direction only.

Examiner insight

“Many of those who realised that it was a valve gave insufficient detail for its function, saying that it controlled the flow of blood, but did not say that it prevented the blood flowing backwards.” “Some candidates incorrectly identified capillaries as having valves.”

Worked example 12 marks

The circulatory system includes valves. State the function of the valves.

1
valves prevent backflow of blood [1]
2
so that blood flows in one direction only [1]

2. Single circulation of a fish

In a fish, blood passes through the heart once in each complete circuit of the body. This is a single circulation.

The blood passes through the gill capillaries and the body capillaries before it returns to the heart.

Examiner insight

“Many used the term ‘simple’ for the circulatory system of fish.” “Answers that simply stated blood flows through the heart once were too vague and could not be credited.”

Worked example 12 marks

A fish has a single circulation. Explain what this means.

1
blood flows through the heart once [1]
2
in each complete circuit of the body [1]

3. Double circulation of a mammal

In a mammal, blood passes through the heart twice in one complete circuit of the body. This is a double circulation.

There are two circuits, joined at the heart. The pulmonary circuit carries blood from the heart to the lung capillaries and back to the heart. The systemic circuit carries blood from the heart to the body capillaries and back to the heart.

Examiner insight

“Other errors included the implication that there were two independent circulatory systems or that blood flowed twice through the body in a single circulation.” “Some candidates could deduce that the blood would flow through the heart twice but needed to specify this as happening in one complete circulation.”

Worked example 11 mark

What is a double circulation?

A Blood circulates through arteries and veins.

B Blood circulates through two hearts.

C Blood flows through the heart twice for each circulation.

D Blood flows twice around the body before going to the lungs.

1
C: blood flows through the heart twice for each circulation. [1]

4. Advantages of a double circulation

Oxygenated and deoxygenated blood are kept separate. Blood can be transported at high pressure around the body. This increases the efficiency of supplying oxygen to cells for aerobic respiration.

The pressure through the lungs is lower, which protects their delicate capillaries. A double circulation also supports a high metabolic rate and a large size.

Examiner insight

“Some answers relating to blood pressure were negated by the suggestion that high pressure would be maintained in both loops.” “Rarely were the advantages of low-pressure blood through the lungs made clear; more often candidates only explained that blood at high pressure leads to a good supply of oxygen to the body.”

Worked example 14 marks

Complete the sentences about the human circulatory system.

In a human, blood passes through the heart ........ during one complete circuit of the body.

This type of circulatory system is called a ........ circulation.

An advantage of this type of circulatory system is that blood can be transported at ........ pressure around the body. This increases the efficiency of supplying oxygen molecules to cells for ........ to release energy.

1
twice / two (times) [1]
2
double [1]
3
high(er) [1]
4
(aerobic) respiration [1]

Recap

Circulatory system: blood vessels, a pump (the heart) and valves.
Valves prevent backflow, so blood flows one way.
Extended: fish have a single circulation. Blood passes through the heart once in each circuit.
Extended: mammals have a double circulation. Blood passes through the heart twice in one circuit.
Extended: double circulation keeps oxygenated and deoxygenated blood separate.
Extended: it gives high pressure around the body for faster delivery of oxygen for respiration.

5. Heart structures and blood vessels

The heart has a muscular wall. Inside, the septum separates the left and right ventricles. Each side has an atrium and a ventricle. One-way valves keep the blood flowing in one direction. The coronary arteries supply the heart muscle with oxygen.

Blood is pumped away from the heart in arteries. It returns to the heart in veins.

The vena cava carries blood to the right atrium. The left ventricle pumps blood into the aorta. The pulmonary vein returns blood from the lungs to the heart.

Examiner insight

“Candidates were asked to name a heart chamber (the right ventricle) but the majority named a blood vessel. Candidates need to be clear that the heart is responsible for pumping the blood, whereas the role of a blood vessel is to transport the blood.” “A significant proportion of candidates did not appreciate that it is the left ventricle that pumps blood to the aorta.”

Worked example 11 mark

Which blood vessel carries blood to the right atrium of the heart?

A aorta

B coronary artery

C pulmonary vein

D vena cava

1
blood returns to the heart in veins, so the aorta and the coronary artery are not the answer
2
answer D: the vena cava [1]

6. Monitoring the heart and the effect of activity

The activity of the heart may be monitored by an ECG, by pulse rate and by listening to the sounds of valves closing.

To investigate the effect of physical activity, count the pulse in a set time at rest. Repeat straight after activity and compare. The pulse rate is higher after activity.

A valve makes a sound when it closes, not when it opens.

heart rate = (number of beats)/(time in minutes)

Examiner insight

“Many described taking the pulse rate, although a significant number omitted the word ‘rate’ and so were not awarded the mark.” “Several were able to calculate the time taken for one beat, but were unable to convert this to the correct heart rate.”

Worked example 11 mark

A complete heartbeat occurs when all four muscular walls of the heart complete their contraction.

In a baby, it takes 0.4 seconds for one complete heartbeat.

How many times does the baby’s heart beat in one minute?

A 0.4 B 24 C 150 D 240

1
one minute = 60 s, so beats per minute = 60 ÷ 0.4 = 150
2
answer C [1]

7. Coronary heart disease

Coronary heart disease is the blockage of coronary arteries. These are the arteries that supply the heart muscle with oxygen.

The risk factors are diet, lack of exercise, stress, smoking, genetic predisposition, age and sex. A risk factor raises the chance of the disease. It is not a symptom.

Diet and exercise are risk factors a person can change. Avoiding fatty foods and taking exercise are ways to prevent a blockage.

Examiner insight

“Many candidates did not know what was meant by risk factors. Many respond by stating the consequences of having a blockage in the coronary arteries. There was a tendency for the answers to be too vague.” “Few candidates specified the coronary artery. Incorrect responses included artery, vein and the blood vessels to or from the heart.”

Worked example 11 mark

In a patient with coronary heart disease, which blood vessel would become blocked?

A aorta

B coronary artery

C coronary vein

D pulmonary artery

1
coronary heart disease is the blockage of coronary arteries
2
answer B: the coronary artery [1]

8. Valves and the action of the heart

The heart has two kinds of valve: atrioventricular valves and semilunar valves. An atrioventricular valve lies between an atrium and a ventricle.

The muscle of the atria and ventricles contracts to pump the blood. Blood flows from an atrium into a ventricle through a valve. Valves prevent backflow, so the blood moves in one direction only.

The atrioventricular valves and the semilunar valves are not both open at the same time.

Examiner insight

“Candidates should be reminded to use the correctly terminology and describe the atria and ventricles as contracting to pump the blood, rather than just pushing or pumping.” “Many of those who realised that it was a valve gave insufficient detail for its function, saying that it controlled the flow of blood, but did not say that it prevented the blood flowing backwards.”

Worked example 13 marks

(a) Name the valves between the atria and the ventricles.

(b) Name the other type of valve in the heart.

1
(a) atrioventricular valves [1]
2
(b) semilunar valves [1]
3
(c) they prevent blood flowing backwards, so blood flows in one direction [1]

9. Thickness of the heart walls

The walls of the ventricles are thicker than the walls of the atria. The wall of the left ventricle is thicker than the wall of the right ventricle.

Both ventricles pump blood at high pressure. The left ventricle pumps it at a higher pressure and over a greater distance. The thicker wall is there to pump the blood. It is not there to withstand the pressure.

Examiner insight

“A common misconception was that the right ventricle pumped the blood at low pressure whereas the left ventricle pumped the blood at high pressure. Both ventricles pump the blood at high pressures, however, the left ventricle pumps the blood at a higher pressure.” “Many candidates explained the differences between the thickness of the two ventricles in terms of the distance blood travels and the pressure needed in each of the circuits – pulmonary and systemic. However, a significant minority stated that the thicker walls were needed to withstand the high pressure of blood in the heart and to prevent damage in the heart.”

Worked example 11 mark

Atria and ventricles are chambers in the heart.

Which statements describe the relative thickness of the muscle walls of these chambers?

1 The walls of the atria are thicker than the walls of the ventricles.

2 The walls of the ventricles are thicker than the walls of the atria.

3 The wall of the left ventricle is thicker than the wall of the right ventricle.

4 The wall of the right ventricle is thicker than the wall of the left ventricle.

A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4

1
statements 2 and 3 are correct: the ventricle walls are thicker than the atria, and the left ventricle is thicker than the right
2
answer C [1]

10. The septum

The septum is the muscular wall between the left and right sides of the heart. It is important because it separates oxygenated and deoxygenated blood.

Blood does not cross the septum. If there is a hole in the septum, oxygenated and deoxygenated blood mix and the transport of oxygen decreases.

The septum does not pump blood, and it is not a valve.

Examiner insight

“Fewer gave the function as separating the oxygenated and deoxygenated blood. Common errors were to write about the pumping action of the heart and the role of valves in preventing backflow.” “A common misconception was to suggest that the septum is used to push blood through the heart.”

Worked example 12 marks

Name the structure that separates the left and right ventricles. Explain why this structure is important.

1
the septum [1]
2
it separates oxygenated and deoxygenated blood [1]

11. Why heart rate rises with activity

During physical activity the heart rate increases. The muscles contract more, so they need more energy. Aerobic respiration releases this energy and needs oxygen, so the heart beats faster. More blood flows to the muscles and supplies them with oxygen.

The hormone adrenaline also increases heart rate.

After activity the heart rate stays high for a time. The body is removing an oxygen debt. Respiration releases energy: it does not produce it.

Examiner insight

“Most realised that the heart rate increased, but weaker responses only related it to a demand for extra energy or oxygen without also connecting this to respiration and muscle contraction. Candidates should be reminded that the process of respiration releases energy and does not produce energy.” “Candidates often stated that there was more blood flow, but they did not state that this occurs to the muscles.”

Worked example 14 marks

The heart rate of a horse was monitored before, during and after a race. Figure 4.1 shows the results.

Explain why the heart rate does not immediately return to its resting value after the race ends in Figure 4.1.

1
correct reference to oxygen debt [1]
2
anaerobic respiration occurs [1]
3
build-up of lactic acid in the muscles / blood [1]
4
transport of lactic acid / oxygen in the blood to the liver [1]
5
(a fifth point: lactic acid is broken down using oxygen. Only four marks are available.)

Recap

Blood is pumped away from the heart in arteries and returns in veins.
The heart is monitored by ECG, pulse rate and the sounds of valves closing.
Heart rate = number of beats ÷ time in minutes.
Coronary heart disease is the blockage of coronary arteries. A risk factor raises the chance, it is not a symptom.
Extended: valves prevent backflow. Atria and ventricles contract to pump blood.
Extended: ventricle walls are thicker than atria walls, and the left is thicker than the right (higher pressure, greater distance).
Extended: the septum separates oxygenated and deoxygenated blood.
Extended: activity raises heart rate for more aerobic respiration. It stays high afterwards while the oxygen debt is removed.

12. Structure of the three blood vessels

An artery has a thicker wall and a narrower lumen than a vein. A capillary has a wall that is one cell thick and a narrow lumen.

Only veins have valves. Arteries and capillaries have none.

Always compare like with like: write "the wall of a vein is thinner", not "veins are thinner".

Examiner insight

“Few correctly selected option A, with many candidates incorrectly believing that capillaries and arteries have valves.” “Some candidates incorrectly believed that arteries have large lumens.”

Worked example 13 marks

State three structural differences between an artery and a vein.

1
an artery has a thicker wall than a vein [1]
2
an artery has a narrower lumen than a vein [1]
3
a vein has valves, an artery does not [1]

13. Functions of capillaries

Capillaries are the vessels where blood and cells exchange substances. They take blood close to cells, so that they supply all the cells of the body.

Substances cross the capillary wall by diffusion. Oxygen diffuses out of the blood into the body cells. Carbon dioxide diffuses from the cells into the blood.

Examiner insight

“Most candidates described the features of capillaries, but fewer were able to go on and describe how these features were useful to the function of the capillary.”

Worked example 12 marks

State two functions of capillaries.

1
exchange of substances between the blood and the cells [1]
2
take blood close to cells / supply all the cells [1]

14. Vessels to and from the heart, lungs and kidney

An artery carries blood away from the heart. A vein carries blood towards the heart. So blood leaves the heart in the aorta and the pulmonary artery, and enters it from the vena cava and the pulmonary vein.

The pulmonary artery takes blood to the lungs. The pulmonary vein brings oxygenated blood from the lungs to the heart. The renal artery takes blood to the kidney. The renal vein takes blood away from it.

The aorta, the pulmonary vein and the renal artery all carry oxygenated blood.

Examiner insight

“Many candidates recalled that the blood vessel that returns blood from the lungs to the heart is the pulmonary vein. The pulmonary artery was the commonest incorrect response.” “Most candidates could identify renal as being the name of vessels to or from the kidney, but fewer correctly chose vein as the vessel transporting blood away from the kidney with many choosing artery.”

Worked example 11 mark

Which row shows what is carried, and in which direction, by the pulmonary vein?

	what is carried	direction
A	deoxygenated blood	from the heart
B	deoxygenated blood	to the heart
C	oxygenated blood	from the heart
D	oxygenated blood	to the heart

1
D: a vein carries blood to the heart. It comes from the lungs, so the blood is oxygenated. [1]

15. Artery and vein structure and blood pressure

Blood in an artery is at high pressure. An artery has a thick wall to withstand the high pressure of the blood. Its wall also contains elastic fibres.

Blood in a vein is at low pressure, so a thinner wall is enough. Valves in a vein prevent the blood flowing backwards.

Examiner insight

“To gain each marking point candidates were required to state the structural adaptation and explain its importance.” “A common error was to say that elastic fibres contract and relax.”

Worked example 13 marks

Explain how the structure of(a) an artery and(b) a vein is related to the pressure of the blood that it transports.

1
(a) an artery has a thick wall to withstand the high pressure of the blood [1]
2
(b) a vein has a thinner wall because the blood is at low pressure [1]
3
a vein has valves to prevent backflow of blood [1]

16. Capillary structure and function

Capillaries form a network of highly branched vessels. This gives a large surface area and takes blood close to every cell.

Their walls are one cell thick, so the diffusion distance is small. The walls are permeable, so substances pass through. The narrow lumen makes red blood cells pass through slowly.

Examiner insight

“Some candidates referred to capillaries as thin rather than having a thin wall.” “A few candidates described the lumen of capillaries as being wide rather than narrow.”

Worked example 15 marks

Explain how the structure of capillaries is related to their functions.

1
capillaries form a network / are highly branched [1]
2
giving an increased surface area [1]
3
walls are one cell thick [1]
4
so the diffusion distance is small [1]
5
the lumen is narrow, so red blood cells pass through slowly [1]

17. Main blood vessels of the liver

Three main vessels join the liver: the hepatic artery, the hepatic veins and the hepatic portal vein.

The hepatic portal vein is a vein. It is not the artery that takes blood to the digestive system.

Examiner insight

“The most common incorrect blood vessel identified was D, the artery transporting blood to the digestive system.”

Worked example 13 marks

Name the three main blood vessels to and from the liver.

1
hepatic artery [1]
2
hepatic veins [1]
3
hepatic portal vein [1]

Recap

Artery: thicker wall, narrower lumen. Vein: thinner wall, wider lumen, valves.
Capillary: wall one cell thick, narrow lumen, no valves.
Capillaries exchange substances between the blood and the cells.
Arteries carry blood away from the heart. Veins carry blood towards it.
Pulmonary vein: oxygenated blood to the heart. Renal vein: blood away from the kidney.
Extended: a thick artery wall withstands high pressure. Valves in veins prevent backflow.
Extended: link each capillary feature (network, thin wall, narrow lumen) to exchange.
Extended: liver vessels are the hepatic artery, hepatic veins and hepatic portal vein.

18. Components of blood

Blood has four components: red blood cells, white blood cells, platelets and plasma.

Red blood cells have no nucleus. White blood cells have a nucleus, so a nucleus tells the two cells apart on a photomicrograph or diagram.

Haemoglobin, oxygen and water are not extra components. They are found inside the red blood cells or the plasma.

Examiner insight

“The presence of a nucleus identifies the cell as a white blood cell. Some detail of the role of each cell is needed, rather than just protection or transport.” “Many named haemoglobin, oxygen or water, but these are constituents of red blood cells and plasma rather than a component of blood.”

Worked example 15 marks

(a) List the four components of blood.

(b) A photomicrograph shows one blood cell with a nucleus and one without. Name the cell that has a nucleus.

1
(a) red blood cells [1]
2
white blood cells [1]
3
platelets [1]
4
plasma [1]
5
(b) the cell with a nucleus is a white blood cell [1]

19. Red blood cells and haemoglobin

Red blood cells transport oxygen. Their cytoplasm contains haemoglobin, which carries the oxygen.

Haemoglobin is not dissolved in the plasma. A question that asks for the function wants the transport of oxygen, not a description of the cell.

Examiner insight

“Many candidates appeared to believe that haemoglobin is dissolved in blood plasma.” “A few candidates described that it would contain haemoglobin or was biconcave in shape, rather than giving its function.”

Worked example 12 marks

State the function of red blood cells. Name the substance inside them that is needed for this function.

1
transport of oxygen [1]
2
haemoglobin [1]

20. White blood cells

White blood cells defend the body against pathogens in two ways. They carry out phagocytosis and they carry out antibody production.

An answer needs both functions. A vague word such as protection or fighting infection is not enough.

Examiner insight

“Usually, these candidates linked only one function to white blood cells, often antibody production.”

Worked example 11 mark

Which row shows how white blood cells help to defend the body against pathogens?

row	antibody production	blood clotting	phagocytosis
A	no	no	yes
B	no	yes	no
C	yes	no	yes
D	yes	yes	no

1
C: white blood cells carry out antibody production and phagocytosis, not blood clotting [1]

21. Platelets and the roles of clotting

Platelets are involved in blood clotting. The details are not required at Core.

Clotting has two roles. It prevents blood loss and it prevents the entry of pathogens.

Platelets do not carry oxygen and do not make antibodies.

Examiner insight

“The question asked for the roles of blood clotting. Some candidates described how blood clots or how blood travels around the body.” “Many candidates understood that blood clotting is slower than normal in a person with very few platelets. Some candidates incorrectly believed that antibody formation would be slower than normal.”

Worked example 11 mark

A patient has a blood test and the platelet count is found to be lower than usual. Which effect will this have?

A Blood clotting at a cut will take longer.

B Fewer antibodies will be produced if microbes enter the bloodstream.

C Nutrient transport around the body will be restricted.

D Less oxygen will be carried to body cells.

1
A: platelets are needed for clotting, so clotting at a cut takes longer [1]

22. Plasma

Plasma is the liquid part of the blood. Its function is the transport of blood cells, ions, nutrients, urea, hormones and carbon dioxide.

A statement of function names what is transported. Saying that plasma is a liquid does not.

Plasma is not cytoplasm. It is not the fluid inside cells.

Examiner insight

“Many candidates gave its function as being the liquid part of the blood or thought that plasma was responsible for blood clotting.” “Some confused plasma with cytoplasm saying that it is the fluid inside cells.”

Worked example 13 marks

State the function of plasma. Name two substances that it carries.

1
transport (in the blood) [1]
2
one correct substance, such as urea [1]
3
a second correct substance, such as hormones [1]

23. Lymphocytes and phagocytes

Lymphocytes and phagocytes are two types of white blood cell. At Extended, name the type: white blood cell alone is too vague.

Lymphocytes carry out antibody production. Phagocytes carry out phagocytosis: they engulf pathogens.

On a photomicrograph or diagram both have a nucleus, which red blood cells lack. Tell the two apart by the appearance of the nucleus, not by the shape of the cell.

Examiner insight

“Many candidates incorrectly believed that component A (the phagocyte) makes antibodies.” “Many candidates stated the function of lymphocytes as the production of antibodies, although some confused them with phagocytes stating that lymphocytes ‘engulf pathogens’.”

Worked example 11 mark

Which component of blood carries out phagocytosis?

A plasma

B platelets

C red blood cells

D white blood cells

1
D: phagocytes, which engulf pathogens, are white blood cells [1]

24. How blood clots

Clotting is the conversion of fibrinogen to fibrin to form a mesh.

Fibrinogen is a protein found in the plasma. Fibrin is the product, and the structure it forms is a mesh.

Examiner insight

“Some candidates were unsure whether fibrinogen is converted to fibrin or whether fibrin is converted to fibrinogen. During blood clotting, fibrinogen is converted to fibrin.” “Others did not adequately refer to the nature of the structure formed by fibrin, describing it simply as ‘fibres’.”

Worked example 13 marks

(a) Describe the process of blood clotting.

(b) State one role of blood clotting.

1
fibrinogen is converted to fibrin [1]
2
the fibrin forms a mesh [1]
3
(b) prevents blood loss, or prevents the entry of pathogens [1]

Recap

Blood: red blood cells, white blood cells, platelets and plasma.
Red blood cells have no nucleus and transport oxygen using haemoglobin.
White blood cells: phagocytosis and antibody production.
Platelets are involved in clotting. Clotting prevents blood loss and the entry of pathogens.
Plasma transports blood cells, ions, nutrients, urea, hormones and carbon dioxide.
Extended: lymphocytes produce antibodies. Phagocytes engulf pathogens by phagocytosis.
Extended: clotting is the conversion of fibrinogen to fibrin to form a mesh.

End-of-chapter exercise

Test yourself on the whole chapter. Work through these before moving on.

Name the organ that acts as the pump in the circulatory system.1 mark
The circulatory system is made of three parts. Name them.3 marks
A student says: “Valves control the flow of blood.” Rewrite this so that it would gain full credit.2 marks
A student writes: “A fish has a simple circulation. Blood flows through the heart once.” Give two corrections that this answer needs.2 marks
Describe the single circulation of a fish. Start at the heart.3 marks
Define the term double circulation.2 marks
Describe the double circulation of a mammal.3 marks
A cheetah has a very high metabolic rate when it sprints. Explain how its double circulation helps its muscle cells to release energy.4 marks
Scientists measured the blood pressure at three places in the circulatory systems of two animals, P and Q. One animal has a single circulation and the other has a double circulation. The results are in the table below. (a) State which animal has the double circulation. Use the data to explain your answer. [3] (b) Use the data to explain two advantages of the circulation of this animal. [3] | Place where pressure was measured | Animal P / kPa | Animal Q / kPa | | --- | --- | --- | | blood leaving the heart for the gas exchange surface | 5.0 | 3.3 | | blood leaving the gas exchange surface | 3.2 | 1.0 | | blood entering the body capillaries | 3.1 | 16.0 |6 marks
In animal R, blood passes through the heart twice in one complete circuit of the body. Unlike a mammal, the heart of R has only one ventricle. Oxygenated blood from the lungs and deoxygenated blood from the body mix in this ventricle. The ventricle then pumps blood to the lungs and to the body at the same pressure. (a) State the type of circulation in animal R. Give a reason. [2] (b) Explain why the cells of R are supplied with oxygen less efficiently than the cells of a mammal. [3] (c) Suggest why the ventricle of R cannot pump blood at a very high pressure without causing harm. [1]6 marks
Complete the sentence. Blood is pumped away from the heart in ______ and returns to the heart in ______.2 marks
State two ways, other than an ECG, in which the activity of the heart may be monitored.2 marks
A student counts 18 heartbeats in 15 s. Calculate her heart rate in beats per minute.2 marks
A student measured her pulse rate before and after running for 2 minutes. (a) Calculate the increase in pulse rate caused by running. (b) Describe the effect of the running on her pulse rate, using the data. | Time of measurement | Pulse rate / beats per minute | | --- | --- | | at rest | 72 | | straight after running | 138 | | 5 minutes after stopping | 90 |4 marks
Coronary heart disease is caused by a blockage in one type of blood vessel. Name the vessel and state two risk factors for the disease.3 marks
A doctor advises a patient to eat less fatty food and to take regular exercise. Explain how this advice reduces the patient's risk of coronary heart disease.3 marks
A student writes: ‘The walls of the atria are thicker than the walls of the ventricles. The wall of the right ventricle is thicker than the wall of the left ventricle.’ Correct both mistakes and give a reason for the second.3 marks
Describe how blood is moved from an atrium into a ventricle and then out of the heart. Use the name of a valve in your answer.4 marks
A baby is born with a hole in the septum. Each time the ventricles contract, some blood passes through the hole from the left ventricle into the right ventricle. (a) Explain why the blood passes through the hole in this direction. (b) Explain why the hole decreases the transport of oxygen to the body.5 marks
The table gives ECG data for a rower before and after a test on a rowing machine. (a) Calculate the heart rate in beats per minute at the end of the test and 5 minutes after. (b) Calculate the percentage change in heart rate between these two times. (c) Explain why the heart rate at the end of the test is higher than at rest. (d) Explain why the heart rate is still above its resting value 5 minutes after the test. | Time of measurement | Time for one heartbeat / s | | --- | --- | | at rest | 1.00 | | end of the test | 0.40 | | 5 minutes after the test | 0.50 |9 marks
Name the blood vessel that carries blood from the heart to the lungs.1 mark
Name the blood vessel that carries blood away from the kidney.1 mark
Carbon dioxide made by muscle cells enters a nearby capillary. Name the process and state the function of capillaries that this shows.2 marks
A student says that arteries have valves to stop blood flowing backwards. Name the type of vessel that really has valves and state one other way its structure differs from an artery.2 marks
A student lists the aorta, the pulmonary artery and the renal artery as three vessels that carry oxygenated blood. State which vessel is wrong and name the vessel that should replace it.2 marks
Vessel P has a thick wall, a narrow lumen and no valves. Vessel Q has a wall one cell thick and no valves. Vessel R has a thin wall, a wide lumen and valves. Identify P, Q and R.3 marks
Explain why the wall of an artery is thicker than the wall of a vein.3 marks
A capillary has a narrow lumen and a wall one cell thick. Explain how each feature is related to exchange.2 marks
The table describes three blood vessels by where each one carries blood from and to. (a) Name vessels J, K and L. [3] (b) A student writes: "J and K are both arteries, because each one carries blood to an organ." Explain the mistake and state which vessel is an artery. [2] | vessel | carries blood from | carries blood to | | --- | --- | --- | | J | aorta | liver | | K | digestive system | liver | | L | liver | vena cava |5 marks
The table gives measurements of three blood vessels, X, Y and Z, from the same organ. (a) Identify X, Y and Z. Give evidence from the table for each. [3] (b) Explain how the walls of X and Y are each related to the pressure of the blood. [2] (c) A student writes: "Z is thin, so blood diffuses out of it quickly." Rewrite the sentence so that it earns the marks. [2] | vessel | wall thickness / mm | lumen diameter / mm | blood pressure / kPa | | --- | --- | --- | --- | | X | 1.0 | 4.0 | 12.0 | | Y | 0.5 | 5.0 | 1.0 | | Z | 0.001 | 0.008 | 3.0 |7 marks
List the components of blood.4 marks
State the function of red blood cells and the role of haemoglobin in it.2 marks
A cell in a photomicrograph of blood has no nucleus. Name the cell and state its function.2 marks
State two functions of white blood cells.2 marks
State the function of platelets and the effect of a low platelet count when a person is cut.2 marks
Name the component of blood that transports hormones. State two other things it transports.3 marks
The table gives blood test results for four people, as percentages of the normal count. (a) Name the person whose blood will transport less oxygen than normal and will also clot more slowly than normal. (b) Give two reasons for your choice. (c) State the two roles of blood clotting. | person | red blood cells | white blood cells | platelets | | --- | --- | --- | --- | | P | 100 | 45 | 100 | | Q | 60 | 100 | 100 | | R | 100 | 100 | 30 | | S | 55 | 100 | 35 |5 marks
Correct this statement: ‘Lymphocytes engulf pathogens and phagocytes make antibodies.’2 marks
A woman's plasma contains no fibrinogen. Her platelet count is normal. (a) Explain why her blood does not clot at a cut. (b) Use the roles of blood clotting to state two dangers to her at the cut. (c) A student says she will also make fewer antibodies. Explain why the student is wrong.6 marks
The table gives counts in 1 mm³ of blood for a healthy adult and for patients X and Y. (a) Calculate the percentage decrease in lymphocytes from the healthy adult to patient X. (b) A student says patient X cannot make antibodies. Use the table to explain the mistake. (c) Bacteria get into a cut on patient Y. Use the table to explain two reasons why Y is less well defended than the healthy adult. (d) State, with a reason, whether patient Y makes far fewer antibodies than the healthy adult. | component | healthy adult | patient X | patient Y | | --- | --- | --- | --- | | lymphocytes | 2500 | 500 | 2400 | | phagocytes | 4500 | 4400 | 900 | | platelets | 250 000 | 240 000 | 60 000 |9 marks

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1. The circulatory system#

2. Single circulation of a fish#

3. Double circulation of a mammal#

4. Advantages of a double circulation#

5. Heart structures and blood vessels#

6. Monitoring the heart and the effect of activity#

7. Coronary heart disease#

8. Valves and the action of the heart#

9. Thickness of the heart walls#

10. The septum#

11. Why heart rate rises with activity#

12. Structure of the three blood vessels#

13. Functions of capillaries#

14. Vessels to and from the heart, lungs and kidney#

15. Artery and vein structure and blood pressure#

16. Capillary structure and function#

17. Main blood vessels of the liver#

18. Components of blood#

19. Red blood cells and haemoglobin#

20. White blood cells#

21. Platelets and the roles of clotting#

22. Plasma#

23. Lymphocytes and phagocytes#

24. How blood clots#

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Chapter at a Glance

Free notes are just the start.

Related chapters

1. The circulatory system

2. Single circulation of a fish

3. Double circulation of a mammal

4. Advantages of a double circulation

5. Heart structures and blood vessels

6. Monitoring the heart and the effect of activity

7. Coronary heart disease

8. Valves and the action of the heart

9. Thickness of the heart walls

10. The septum

11. Why heart rate rises with activity

12. Structure of the three blood vessels

13. Functions of capillaries

14. Vessels to and from the heart, lungs and kidney

15. Artery and vein structure and blood pressure

16. Capillary structure and function

17. Main blood vessels of the liver

18. Components of blood

19. Red blood cells and haemoglobin

20. White blood cells

21. Platelets and the roles of clotting

22. Plasma

23. Lymphocytes and phagocytes

24. How blood clots