AQA GCSE Combined Science (8464), Higher tier · Biology › Organisation › Animal tissues, organs and organ systems
Practise The heart and blood vessels. 15 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How the heart pumps blood around a double circulatory system, how the lungs are adapted for gas exchange, what the pacemaker does, and how arteries, veins and capillaries are adapted to their functions. Questions include labelling the heart, tracing the path of blood, explaining adaptations and calculating the rate of blood flow.
Grade by grade
What you need to be able to do, from the first marks up to the top grade.
3
Name the three types of blood vesselArteries carry blood away from the heart, veins carry blood back to the heart, and capillaries link them inside tissues.
4
Label the heart's chambers and main vesselsRight and left atria and ventricles, the vena cava, pulmonary artery, pulmonary vein, aorta and coronary arteries.
5
Describe the double circulatory systemThe right ventricle pumps blood to the lungs and the left ventricle pumps blood around the rest of the body.
5
Describe the role of the pacemakerA group of cells in the right atrium controls the natural resting heart rate; an artificial pacemaker is an electrical device that corrects an irregular heart rate.
6
Explain how blood vessels suit their functionsArteries have thick muscular, elastic walls for high pressure, veins have valves, and capillary walls are one cell thick for diffusion.
6
Calculate the rate of blood flowRate of blood flow = volume of blood ÷ time, e.g. in cm3 per minute.
7
Explain how alveoli are adapted for gas exchangeMillions of alveoli give a large surface area, with thin walls and a rich capillary network keeping a steep concentration gradient.
7
Explain why the left ventricle wall is thickerIt pumps blood at a higher pressure all round the body, while the right ventricle only pumps blood to the nearby lungs.
Notes
The heart and double circulation
The heart is an organ, made mainly of muscle, that pumps blood. It has two atria at the top and two ventricles below.
Blood flows: vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta → body.
This is a double circulatory system. The right ventricle pumps blood to the lungs, where gas exchange takes place. The left ventricle pumps blood around the rest of the body.
The left ventricle has a thicker muscular wall because it pumps blood at a higher pressure, all the way round the body. grade 7+
Valves stop blood flowing backwards (you do not need their names).
The coronary arteries branch off the aorta and supply the heart muscle itself with oxygenated blood.
Heart rate
The natural resting heart rate is controlled by a group of cells in the right atrium that act as a pacemaker.
An artificial pacemaker is an electrical device fitted to correct irregularities in the heart rate.
The lungs
Air passes down the trachea, into the two bronchi, and on to millions of tiny air sacs called alveoli.
Each alveolus is surrounded by a network of capillaries. Oxygen diffuses from the air in the alveoli into the blood; carbon dioxide diffuses from the blood into the alveoli.
Adaptations: a very large surface area (many alveoli); thin walls, giving a short diffusion distance; a good blood supply and breathing, which keep a steep concentration gradient.
Blood vessels
Arteries carry blood away from the heart at high pressure. They have thick walls containing muscle and elastic fibres, so they withstand the pressure and stretch and recoil with each heartbeat.
Veins carry blood back to the heart at low pressure. They have thinner walls, a wide lumen and valves that stop blood flowing backwards.
Capillaries are tiny vessels that run through tissues. Their walls are one cell thick, giving a short diffusion distance for substances to pass between the blood and the cells.
Rate of blood flow = volume of blood ÷ time.
Cheatsheet
Right side of the heart → lungs; left side → rest of the body
Vena cava → RA → RV → pulmonary artery → lungs → pulmonary vein → LA → LV → aorta
Arteries: away from the heart, high pressure, thick muscular and elastic walls
Veins: back to the heart, low pressure, thin walls, wide lumen, valves
Capillaries: walls one cell thick, short diffusion distance
Coronary arteries: supply the heart muscle with oxygenated blood
Pacemaker: a group of cells in the right atrium
Lungs: trachea → bronchi → alveoli (surrounded by capillaries)
Rate of blood flow = volume of blood ÷ time
How to answer each type of question
Trace the path of blood or label the heart
1 to 4 marks4
The heart is drawn as if you are facing the person, so the right side of the heart is on the left of the page.
Follow the order: vein → atrium → ventricle → artery.
Use the names in the specification: vena cava, pulmonary artery, pulmonary vein, aorta.
Example. Describe the path taken by blood from the vena cava until it leaves the heart on its way to the lungs.
Show the model answer
Vena cava → right atrium (1) → right ventricle (1) → pulmonary artery (1)
Explain how a blood vessel is adapted to its function
2 to 3 marks6
State a feature, e.g. 'wall one cell thick'.
Link it to the function with 'so', e.g. 'so there is a short diffusion distance'.
Give one feature-plus-reason for each pair of marks.
Example. Explain how capillaries are adapted for exchanging substances with body cells.
Show the model answer
The capillary wall is only one cell thick (1), so there is a short diffusion distance (1). There are very many capillaries forming a network, so every cell is close to a capillary / there is a large surface area (1).
Calculate the rate of blood flow
2 marks6
Use rate of blood flow = volume of blood ÷ time.
Convert units first if needed, e.g. seconds to minutes.
Give the unit asked for, e.g. cm3 per minute.
Example. In 15 seconds, 1200 cm3 of blood flowed through the aorta. Calculate the rate of blood flow in cm3 per minute.
Show the model answer
15 s = 0.25 min, so rate = 1200 ÷ 0.25 (1) = 4800 cm3 per minute (1) (or 1200 ÷ 15 = 80 cm3 per second, × 60 = 4800)
Explain how the lungs are adapted for gas exchange
3 to 4 marks7
Surface area: millions of alveoli.
Diffusion distance: thin walls of the alveoli and capillaries.
Concentration gradient: a good blood supply carries oxygen away and brings carbon dioxide, and breathing refreshes the air.
Example. Explain how the alveoli are adapted for efficient gas exchange.
Show the model answer
There are millions of alveoli, giving a very large surface area (1). The walls of the alveoli are thin / one cell thick, so the diffusion distance is short (1). Each alveolus is surrounded by a network of capillaries / has a good blood supply (1). This, with breathing, keeps a steep concentration gradient for oxygen and carbon dioxide (1).
Explain differences between the two sides of the heart
2 marks7
Say where each ventricle pumps blood to.
Link the thicker wall to the higher pressure needed.
Example. The muscular wall of the left ventricle is much thicker than the wall of the right ventricle. Explain why.
Show the model answer
The left ventricle pumps blood all round the rest of the body, but the right ventricle only pumps blood to the lungs (1). So the left ventricle needs more muscle to pump blood at a higher pressure (1).
Shortcuts and memory tricks
Arteries carry blood away from the heart; veins carry it back in.
'Pulmonary' means 'to do with the lungs': the pulmonary artery goes to the lungs and the pulmonary vein comes back from them.
Vessels are named by direction, not oxygen: the pulmonary artery carries deoxygenated blood and the pulmonary vein carries oxygenated blood.
Blood always goes into an atrium first, then a ventricle: A before V, like the alphabet.
The left side works harder (it pumps to the whole body), so the left side has the thicker wall.
Where marks are lost
Mixing up left and right on a diagram. The heart is drawn as if you are facing the person.
Saying arteries always carry oxygenated blood and veins always carry deoxygenated blood. The pulmonary vessels do the opposite.
Writing only 'thin walls' for capillaries when 'walls one cell thick' is the precise answer, or writing 'cell wall' (animal cells do not have cell walls).
Saying the pacemaker is in the left atrium or in a ventricle. It is in the right atrium.
Saying the heart muscle gets its oxygen from the blood inside its chambers. It is supplied by the coronary arteries.
Forgetting to convert seconds to minutes in blood flow calculations.
Exam technique
In adaptation questions, link each feature to its function: feature + 'so' + reason.
Use the vessel names exactly: vena cava, pulmonary artery, pulmonary vein, aorta, coronary arteries.
In calculations, check which unit the question asks for and show your working.
For lung questions, use the terms surface area, diffusion distance and concentration gradient.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Name the blood vessel that carries blood from the heart to the rest of the body.
aorta
Name the blood vessel that carries deoxygenated blood from the heart to the lungs.
pulmonary artery
The natural resting heart rate is controlled by a group of cells called the pacemaker. Where in the heart is the pacemaker found?
right atrium
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
The heart pumps blood around the body.
(a) Which chamber of the heart pumps blood to the lungs? Tick (✓) one box.[1]
Left atrium
Left ventricle
Right atrium
Right ventricle
(b) Name the blood vessel that carries blood from the heart to the rest of the body.[1]
(c) Name the blood vessel that carries blood from the body back to the heart.[1]
(d) Name the blood vessels that supply the heart muscle with oxygen.[1]
(e) Humans have a double circulatory system. What does this mean?[1]
Show the answer and mark scheme
(a)Answer: Right ventricle
(b)Answer: aorta
aorta
(c)Answer: vena cava
vena cava
(d)Answer: coronary arteries
coronary arteries
(e)
blood passes through the heart twice for each complete circuit of the body / one circuit goes to the lungs and one to the rest of the body
Question 2Medium7 marks
A student counted 18 pulse beats in 15 seconds while resting.
(a) Calculate the student's resting heart rate in beats per minute.[1]
(b) With each beat, the student's left ventricle pumps 70 cm3 of blood. Calculate the volume of blood pumped by the left ventricle in one minute. Give your answer in dm3.[2]
(c) The student has a total blood volume of 5.5 dm3. Calculate the time taken for the left ventricle to pump a volume of blood equal to the total blood volume. Give your answer in seconds.[2]
(d) Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.[2]
Show the answer and mark scheme
(a)Answer: 72 beats per minute
(18 × 4 =) 72
(b)Answer: 5.04 dm3
72 × 70 = 5040 (cm3)
5.04 (dm3)
(c)Answer: 65 s (65.5) s
5.5 ÷ 5.04 = 1.09 (minutes)
65 – 66 (s)
(d)
the left ventricle pumps blood around the rest of the body, but the right ventricle pumps blood only to the lungs
so the left ventricle must produce a higher pressure / needs more muscle
Question 3Hard8 marks
Gas exchange takes place in the alveoli of the lungs. A pair of human lungs contains about 4.8 × 108 alveoli. Each alveolus can be modelled as a sphere with a diameter of 0.2 mm.
(a) Estimate the total surface area of the alveoli. Surface area of a sphere = \(4\pi r^2\) Give your answer in m2. 1 m2 = 1 000 000 mm2[3]
(b) Other than a large surface area, give two features of the alveoli that make gas exchange efficient.[2]
(c) Describe the pathway taken by a molecule of oxygen from the air outside the body to a red blood cell.[3]
Show the answer and mark scheme
(a)Answer: 60 m2 (60.3) m2
surface area of one alveolus = 4 × π × 0.12 = 0.126 (mm2)
× 4.8 × 108 = 6.0 × 107 (mm2)
60 (m2)
(b)
walls are thin / one cell thick, giving a short diffusion distance
surrounded by a network of capillaries / good blood supply
ventilation (breathing) keeps a high concentration of oxygen in the alveoli / maintains the concentration gradient
moist lining so gases can dissolve
(c)
through the trachea and then a bronchus / bronchi
into an alveolus
diffuses across the alveolus wall and the capillary wall into the blood