Blood and Circulation
Learn the parts of blood and how the heart moves it around the body.
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The circulatory system delivers oxygen and nutrients and removes waste.
In this lesson you will:
- Name the components of blood.
- Describe the double circulation of the heart.
- Explain how exercise affects heart rate.
Blood
Blood has four main parts:
- Plasma — straw-coloured liquid carrying nutrients, hormones and waste.
- Red blood cells — contain haemoglobin and carry oxygen.
- White blood cells — defend the body against infection.
- Platelets — help blood to clot.
The Heart
The heart has four chambers: two atria on top and two ventricles below. Blood goes from the heart to the lungs, back to the heart, then around the body. This is double circulation.
Follow the blood
Right atrium → right ventricle → lungs (picks up oxygen) → left atrium → left ventricle → body.
Arteries carry blood away from the heart; veins carry it back.
Tip Regular exercise strengthens the heart, so it pumps more blood with each beat and rests at a lower rate.
Practice
- Name the four components of blood.
- Why is double circulation important for a mammal?
- Measure your pulse before and after one minute of exercise. Explain the change.
Recap
Blood carries oxygen, nutrients and defences. Double circulation keeps oxygenated and deoxygenated blood separate.
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Course contents
The Human Body
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