Circulation and the heart Cambridge IGCSE Biology (9–1) revision
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In plain words
Your heart is a pump about the size of your fist, and it is really two pumps side by side. The right side sends blood to the lungs to collect oxygen. The left side sends that blood round the rest of the body. So blood goes through the heart twice on every lap.
Three things to know
- Mammals have a double circulation: heart → lungs → heart → body → heart. It keeps the blood at high pressure, so oxygen reaches the tissues quickly. Fish have a single circulation.
- The heart has four chambers: two atria on top, which receive blood, and two ventricles below, which pump it out. Valves stop blood flowing backwards, and the septum keeps the two sides apart.
- The left ventricle has the thicker wall, because it pumps blood all round the body. The coronary arteries supply the heart muscle itself; if they are blocked by fatty deposits, the result is coronary heart disease.
Tips and tricks
- Heart diagrams are drawn as if the person is facing you, so the left side of the heart is on the right of the page.
- Risk factors for coronary heart disease: a diet high in saturated fat, smoking, lack of exercise, stress, age and genes.
It lands in your notebook with its questions as flashcards.
Circulation and the heart: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
How many times does blood pass through the heart on one circuit of the body?
Once on the way to the lungs, and again on the way to the body.
Which chamber has the thickest wall?
It pumps blood round the whole body.
What do the valves in the heart do?
They keep the blood moving one way.
Which vessels supply the heart muscle with blood?
A blockage in one causes a heart attack.
Which of these increases the risk of coronary heart disease?
So do a fatty diet, stress and lack of exercise.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 7 marks. Write your answers on paper, then check them.
Circulation and the heart
Cambridge IGCSE Biology (9–1) 0970 · 7 marks · papermunch.org
Name ______________________________ Date ______________
Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.[2]
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It has more muscle, because it pumps blood at higher pressure all round the body. The right ventricle only pumps blood to the lungs.
State the function of the valves in the heart.[2]
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They stop blood flowing backwards, so it moves in one direction only.
Describe the path of blood from the vena cava to the aorta.[3]
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Right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta.
Answers: Circulation and the heart
- 1. It has more muscle, because it pumps blood at higher pressure all round the body. The right ventricle only pumps blood to the lungs.
- 2. They stop blood flowing backwards, so it moves in one direction only.
- 3. Right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta.