The human body and health
The main organs and their jobs, the skeleton and muscles, digestion, the heart and circulation, and how to stay healthy.
📌 Key points
- Organs have special jobs: the brain controls the body, the heart pumps blood, the lungs take in oxygen, the stomach and intestines digest food, and the kidneys clean the blood.
- The skeleton supports the body, helps us move and protects organs: the skull protects the brain and the ribs protect the heart and lungs.
- Muscles work in pairs. When one contracts (gets shorter), the other relaxes. The biceps bends the arm and the triceps straightens it.
- Food travels through the digestive system: mouth → oesophagus → stomach → small intestine → large intestine.
- Nutrients from food pass into the blood in the small intestine. Water is taken back into the body in the large intestine.
- The heart pumps blood through blood vessels. Arteries carry blood away from the heart and veins carry blood back to it.
- Blood carries oxygen and nutrients to every part of the body and carries waste, such as carbon dioxide, away.
- When you exercise, your heart beats faster (your pulse rate goes up) to get more oxygen to your muscles.
- To stay healthy: eat a balanced diet, exercise, sleep well, keep clean, and avoid smoking and drugs.
📖 Key words
- Organ
- A part of the body with a special job, e.g. the heart.
- Circulation
- The movement of blood around the body, pumped by the heart.
- Artery
- A blood vessel that carries blood away from the heart.
- Vein
- A blood vessel that carries blood back to the heart.
- Digestion
- Breaking food down into small pieces that the body can take into the blood.
- Pulse
- The beat you can feel, e.g. at your wrist, each time the heart pumps blood.
- Nutrients
- The useful substances in food, such as carbohydrates, proteins, fats, vitamins and minerals.
- Balanced diet
- Eating the right amounts of different kinds of food to stay healthy.
✏️ Worked example
Lina’s pulse is 72 beats per minute when she sits still and 130 beats per minute after running for 2 minutes. Explain the change.
- When she runs, her muscles work harder, so they need more oxygen and energy.
- Blood carries oxygen from the lungs to the muscles.
- The heart beats faster to pump more blood, with more oxygen, to the muscles.
- Answer: her pulse rises from 72 to 130 because her heart pumps faster to get more oxygen to her muscles.
When you explain a change in the body, say what the organ does and why the body needs it, e.g. "the heart beats faster to get more oxygen to the muscles".
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