Worked example 1
Which organ system do the heart and blood vessels belong to?
- The heart pumps blood.
- Blood travels through vessels and back.
- This loop is circulation.
Answer: The circulatory system
Science · Foundation
Main organs of the human body and what they do
Organs are body parts with a special job. Organs work together in systems, such as the digestive system or the circulatory system.
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How it works
- Brain: controls the body, thinking and memory, sending messages along nerves.
- Heart: a muscle that pumps blood around the body through blood vessels. Circulatory system.
- Lungs: take oxygen from the air into the blood and remove carbon dioxide. Respiratory system.
- Stomach and intestines: break down food and absorb nutrients. Digestive system.
- Kidneys: filter the blood and make urine. Liver: cleans the blood and helps digestion.
- Skin: the largest organ, protecting the body and helping control temperature.
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Practice questions
Tips
Common mistakes
- Thinking the heart is on the far left — it sits in the middle of the chest, tilted slightly left.
- Thinking the stomach does all of digestion — most nutrients are absorbed in the small intestine.
Last reviewed: 25 September 2026