Question 1
Paper 4 short-answer style1 markName the chamber of the heart that pumps blood to the body. (1 mark)
Model answer
The left ventricle.
Why this scores
One mark for 'left ventricle'.
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Detailed notes on Transport in Animals for Cambridge IGCSE Biology, covering key concepts, explanations, examples, and exam-focused revision points.
A four-chamber muscular pump with valves to stop backflow. Right side handles deoxygenated blood; left side handles oxygenated blood.
Mapped to the Cambridge IGCSE 0610 syllabus (2026-2028).
Four chambers, four valves, four big vessels. Memorise as pairs.
The four chambers (top to bottom; right to left).
| Side | Chamber | Receives blood from | Pumps blood to |
|---|---|---|---|
| Right | Atrium | Vena cava (body) | Right ventricle |
| Right | Ventricle | Right atrium | Pulmonary artery (lungs) |
| Left | Atrium | Pulmonary vein (lungs) | Left ventricle |
| Left | Ventricle | Left atrium | Aorta (body) |
The four big vessels.
The septum. A solid wall of muscle separating the right and left sides. KEEPS oxygenated and deoxygenated blood SEPARATE.
Coronary arteries. Two small arteries branching off the aorta. They wrap around the heart and supply the HEART MUSCLE ITSELF with oxygen + nutrients. Without them, heart cells would die. A blockage causes a HEART ATTACK.
Worked qualitative. Why can't the heart be supplied with oxygen from the blood inside its chambers?
Cambridge tip. When labelling, remember: in the diagram (heart shown as the patient's view), the LEFT side appears on the RIGHT. Don't flip them.
Atria fill → atria contract → ventricles contract → all relax. Heartbeat 'lub-dub' sounds.
One full beat takes ~0.8 seconds at rest.
Stage 1 — Diastole (relaxation, ~0.4 s).
Stage 2 — Atrial systole (~0.1 s).
Stage 3 — Ventricular systole (~0.3 s).
Stage 4 — Diastole again (relaxation).
Heart sounds.
Worked qualitative. What happens if a heart valve fails to close properly (a 'leaky valve')?
Cambridge tip. When asked about valves, always link CLOSURE to BACKFLOW PREVENTION, not active opening. Valves are passive flaps — pressure opens and closes them.
Long route → high pressure → thicker muscle → harder pump.
Compare left vs right ventricle:
| Feature | Right ventricle | Left ventricle |
|---|---|---|
| Wall thickness | Thin (~3 mm) | Thick (~10 mm) |
| Pumps blood to | Lungs only | Whole body |
| Pressure generated | Low (~25 mmHg) | High (~120 mmHg) |
| Distance covered | ~10 cm | ~1-2 m |
The reason.
Atria are thinner-walled than ventricles because they only need to push blood a short distance into the ventricles.
Worked qualitative. Why does living at high altitude (low O₂) sometimes thicken the right ventricle?
Cambridge tip. Always link STRUCTURE (thickness) to FUNCTION (pressure for distance). One-word answers like "stronger" miss the mark.
The heart's own blood supply. Block it = heart attack.
Coronary arteries branch off the AORTA right after it leaves the heart. They wrap around the heart muscle and supply it with oxygen + nutrients.
Why crucial.
Coronary heart disease (CHD).
Risk factors.
Treatment.
Worked qualitative. Why does aspirin help prevent heart attacks?
Cambridge tip. Cambridge often gives a diagram showing the coronary arteries as branches from the aorta. Don't confuse them with the carotid arteries (to the head).
Verbatim phrases and definitions Cambridge mark schemes credit.
Heart appears every Paper 4 (8-12 marks: label diagram, cardiac cycle, valve function, ventricle thickness, coronary disease). Examiner reports flag students confusing pulmonary artery vs vein, saying valves push blood, and weak explanations of why LV is thicker.
Sources: Cambridge IGCSE Biology 0610 syllabus 2026-2028 (9.2); 0610/42 Oct/Nov 2024 — Q7 (cardiac cycle); 0610 Examiner Reports 2022-2024. Last reviewed 2026-05-07.
Step-by-step solutions to past-paper-style questions on heart, written exactly the way a tutor would explain them at the board.
Question
Name the four chambers and the main blood vessels connected to the heart.
Step-by-step solution
Step 1
Right atrium receives deoxygenated blood from the body via the vena cava.
Step 2
Right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery.
Step 3
Left atrium receives oxygenated blood from the lungs via the pulmonary vein.
Step 4
Left ventricle pumps oxygenated blood to the body via the aorta.
Answer
Right atrium ← vena cava; right ventricle → pulmonary artery; left atrium ← pulmonary vein; left ventricle → aorta.
Examiner tip
Cambridge often gives an unlabelled heart diagram. Learn the chamber + vessel pairs.
Question
Name the blood vessel that: (a) brings deoxygenated blood from the body to the heart; (b) carries oxygenated blood from the heart to the body; (c) carries blood from the heart to the lungs; (d) brings blood from the lungs to the heart.
Step-by-step solution
Step 1
(a) From the body to the heart → vena cava.
Step 2
(b) From the heart to the body → aorta.
Step 3
(c) From the heart to the lungs → pulmonary artery.
Step 4
(d) From the lungs to the heart → pulmonary vein.
Answer
(a) Vena cava; (b) aorta; (c) pulmonary artery; (d) pulmonary vein.
Examiner tip
The pulmonary artery (deoxygenated) and pulmonary vein (oxygenated) are the exceptions to the usual artery/vein oxygen rule.
Question
Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.
Step-by-step solution
Step 1
The left ventricle pumps blood through the systemic circulation — all the way around the whole body.
Step 2
This is a long route with high resistance, so a high pressure is needed to push the blood to every part of the body.
Step 3
The right ventricle pumps blood only to the nearby lungs — a short route needing lower pressure.
Step 4
A thicker muscular wall in the left ventricle gives a stronger contraction and so the higher pressure required.
Answer
The left ventricle pumps blood around the whole body (long route, high pressure), so it needs a thicker, more muscular wall than the right ventricle, which only pumps to the nearby lungs.
Question
Explain the function of the atrioventricular valves and the semilunar valves.
Step-by-step solution
Step 1
The atrioventricular (AV) valves lie between the atria and the ventricles.
Step 2
They close when the ventricles contract, preventing blood flowing back into the atria.
Step 3
The semilunar valves lie at the start of the aorta and pulmonary artery.
Step 4
They close when the ventricles relax, preventing blood flowing back into the ventricles from the arteries. Together the valves keep blood moving one way only.
Answer
AV valves stop blood flowing back into the atria; semilunar valves stop blood flowing back into the ventricles. Both ensure one-way flow.
Examiner tip
Valves do not push blood — they only prevent backflow. The muscle contraction provides the push.
Question
Describe one cycle of the heart's beating, including the role of the valves.
Step-by-step solution
Step 1
Diastole: the heart muscle relaxes and the atria fill with blood from the veins.
Step 2
Atrial systole: the atria contract, pushing blood through the open AV valves into the ventricles.
Step 3
Ventricular systole: the ventricles contract; the AV valves close (preventing backflow into the atria) and the semilunar valves open, so blood is pushed out into the aorta and pulmonary artery.
Step 4
Diastole again: the ventricles relax; the semilunar valves close (preventing backflow from the arteries), and the cycle repeats.
Answer
Atria fill (diastole) → atria contract (AV valves open) → ventricles contract (AV valves close, semilunar valves open, blood leaves) → ventricles relax (semilunar valves close). Then repeat.
Question
Explain how and why the heart rate changes during vigorous exercise, and afterwards.
Step-by-step solution
Step 1
During exercise the muscles respire faster, so they need more oxygen and glucose and produce more carbon dioxide.
Step 2
The heart rate increases, pumping blood around the body faster.
Step 3
This delivers oxygen and glucose to the muscles more quickly and removes carbon dioxide faster, supporting the higher rate of respiration. (The hormone adrenaline also raises the heart rate.)
Step 4
After exercise the heart rate stays high for a while to deliver extra oxygen that repays the oxygen debt (removing the lactic acid built up during anaerobic respiration), then returns to normal.
Answer
Heart rate rises during exercise to deliver more oxygen and glucose to the respiring muscles and remove CO₂ faster; it stays raised afterwards to repay the oxygen debt, then returns to resting rate.
Examiner tip
Link the faster heart rate to the muscles' increased respiration and the need to deliver O₂/glucose and remove CO₂.
High-scoring sample answers for heart on the Cambridge IGCSE 0610 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.
Name the chamber of the heart that pumps blood to the body. (1 mark)
Model answer
The left ventricle.
Why this scores
One mark for 'left ventricle'.
Name the blood vessels that carry blood (a) from the heart to the lungs and (b) from the heart to the body. (2 marks)
Model answer
(a) The pulmonary artery carries blood from the heart to the lungs. (b) The aorta carries blood from the heart to the body.
Why this scores
One mark each: pulmonary artery (to lungs); aorta (to body).
Explain why the wall of the left ventricle is thicker than the wall of the right ventricle. (3 marks)
Model answer
The left ventricle has to pump blood all the way around the body (the systemic circulation), which is a long route, whereas the right ventricle only pumps blood to the nearby lungs. The left ventricle therefore needs to produce a higher pressure, so its thicker, more muscular wall gives a stronger contraction to generate that pressure.
Why this scores
Three marks: left pumps to whole body / right to lungs only; left needs higher pressure; thicker muscle gives stronger contraction.
Explain the role of the valves in the heart. (4 marks)
Model answer
The valves make sure blood flows in one direction only through the heart. The atrioventricular valves, between the atria and ventricles, close when the ventricles contract, preventing blood from flowing back into the atria. The semilunar valves, at the base of the aorta and pulmonary artery, close when the ventricles relax, preventing blood from flowing back into the ventricles from the arteries. In this way the valves prevent backflow and keep the blood moving forward.
Why this scores
Four marks: ensure one-way flow; AV valves prevent backflow into atria; semilunar valves prevent backflow into ventricles; valves close at the correct stage.
Describe the cardiac cycle. (5 marks)
Model answer
First, while the heart is relaxed (diastole), blood flows from the veins into the atria. The atria then contract (atrial systole), pushing blood through the open atrioventricular valves into the ventricles. Next the ventricles contract (ventricular systole): the atrioventricular valves close, preventing backflow into the atria, and the semilunar valves open, so blood is forced out into the aorta and pulmonary artery. Finally the ventricles relax, the semilunar valves close to stop blood returning from the arteries, and the cycle begins again.
Why this scores
Five marks: atria fill during diastole; atria contract → blood to ventricles; ventricles contract; AV valves close; semilunar valves open and blood leaves (then close on relaxation).
Explain how and why the heart rate changes during and after a period of vigorous exercise. (6 marks)
Model answer
During vigorous exercise the muscles respire much faster to release the extra energy needed for contraction, so they require more oxygen and glucose and produce more carbon dioxide. To meet this demand, the heart rate increases, pumping blood around the body more quickly. This faster blood flow delivers oxygen and glucose to the muscles more rapidly and removes the carbon dioxide they produce, supporting the higher rate of respiration. (The hormone adrenaline released during exercise also increases the heart rate.) After the exercise stops, the heart rate remains high for a time because the muscles have respired anaerobically and built up lactic acid; the extra oxygen delivered by the continuing fast heart rate is used to break down this lactic acid and repay the oxygen debt. Once the lactic acid has been removed, the heart rate gradually returns to its resting level.
Why this scores
Up to 6 marks: muscles respire faster; need more O₂/glucose, produce more CO₂; heart rate increases; faster delivery of O₂/glucose and removal of CO₂; stays high after exercise to repay oxygen debt/remove lactic acid; returns to resting rate.
Definitions to memorise and the exact keywords mark schemes credit for heart answers — sharpened from recent examiner reports for the 2026 0610 sitting.
Upper chamber of the heart that receives blood from the veins.
Lower, thicker-walled chamber of the heart that pumps blood out into the arteries.
Valve between an atrium and a ventricle. Prevents backflow into the atrium when the ventricle contracts.
Valve at the start of the aorta and pulmonary artery. Prevents backflow into the ventricle when it relaxes.
Branch of the aorta that supplies the heart muscle itself with oxygenated blood.
One complete sequence of heart contraction and relaxation: atrial systole, ventricular systole and diastole.
The traps other students keep falling into on heart questions — taken from recent Cambridge IGCSE 0610 examiner reports and mark schemes — and how to avoid them.
Why it happens
It sounds logical.
How to avoid it
On a standard heart diagram (the heart facing you), the LEFT side of the heart is drawn on the RIGHT of the diagram. Read the labels carefully.
Why it happens
Most veins carry deoxygenated blood.
How to avoid it
The pulmonary vein is the exception — it carries OXYGENATED blood from the lungs to the heart. The pulmonary artery carries deoxygenated blood.
Why it happens
It looks like they help the blood along.
How to avoid it
Valves do NOT push — they only PREVENT BACKFLOW. The contracting heart muscle pushes the blood.
The things students keep getting wrong in this sub-topic, answered.