Lungs & Breathing

Lungs & Breathing

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Lungs & Breathing

Take a deep breath. See how your chest swells. That is because the lungs in your body are taking in air. Lungs are organs in your body that take in oxygen from the air, so that your body can use this oxygen to get its energy. Lungs also send carbon dioxide out of your body. This process, which we call breathing, is a kind of respiration. When you breathe there is an exchange of gases with your surroundings, with oxygen taken in and carbon dioxide sent out. Your body needs oxygen to break down the food you eat and release energy. If you stopped breathing, your body would begin to run out of oxygen, and the tissues in your body would begin to die. Your lungs are very important.

Lungs & Breathing

Most land animals have lungs. Fish collect their oxygen using gills instead (except the lungfish!). You have two lungs inside your chest, one on either side of your heart. They are like two large pink sponges. Your ribs form a kind of cage to protect them.


When you breathe, oxygen from the air is taken into your lungs and from there into your blood. Your heart is a powerful pump. It pushes the blood around your body, and the blood takes the oxygen to all the cells in your body. The blood also collects up waste, including carbon dioxide gas. This is brought back to the lungs, where it can be breathed out. This process happens throughout your life. Let’s look at it a bit more carefully.

Under your ribcage is a very strong muscle called the diaphragm. When the diaphragm contracts (becomes smaller), it opens up space in your chest cavity. Air rushes in, enlarging the lungs to fill this space. This is what is happening when you breathe in, or inhale. There are also muscles between your ribs called intercostal muscles that can make your ribcage expand. You use these, as well as your diaphragm, when you breathe more deeply.

The air enters the body through your nose and mouth. It reaches the lungs through the trachea, or windpipe. The trachea splits into two branches called bronchi, with one going to each lung. Inside the lung, the bronchus (that is, one of the bronchi) divides into smaller and smaller tubes, and ends in tiny air sacs called alveoli. When you inhale, these alveoli fill with air. The alveoli are surrounded by tiny blood vessels called capillaries. These capillaries have very thin walls, so that oxygen can pass (diffuse) through them and into the blood. Blood that has been supplied with oxygen is known as oxygenated blood. This oxygenated blood is taken to the heart and pumped round the body.

Other capillaries surrounding the alveoli contain blood that has done the trip round the body and given up its oxygen. These capillaries are thin-walled veins. They are carrying waste carbon dioxide that they have picked up on their journey. This carbon dioxide diffuses through the thin capillary walls and into the alveoli. When your diaphragm relaxes, the lungs are forced to contract, and the air in the alveoli is pushed out. That is what happens when you breathe out, or exhale.

You probably breathe about 20 times a minute normally. In one breath, a healthy adult takes in between 150 and 250 millilitres of air. That is when you are sitting quietly. If you are exercising, you need much more oxygen. Your breathing becomes faster and deeper. When you are exercising, you may breathe up to 80 times a minute. And you would take in between 3,300 and 5,000 millilitres of air in each breath.


The lungs have fine hairs inside them that help stop dangerous particles and organisms from getting into your blood. But sometimes the air brings bacteria and viruses with it. These can cause lung diseases like pneumonia and tuberculosis.

Many people suffer from asthma. In an asthma attack, the bronchial tubes become narrowed. This makes it hard to breathe. Asthma is often caused by an allergy to pollen, dust or other particles in the surroundings. Fine particles can also cause lungs to become scarred. In the past, people used a material called asbestos in buildings as insulation. Asbestos is now known to be dangerous. Many people who worked with it, breathing in its dust, became ill with asbestosis. Their lungs became thickened and scarred as the dust collected there and breathing became more and more difficult.

Today, the most common severe illness of the lungs is lung cancer. Smoking is the main cause of lung cancer. Tobacco smoke contains many chemicals that can harm cells. Smoking can also cause chronic bronchitis. This is a serious illness in which the bronchi become irritated and swollen.


It is important to look after your lungs. Fresh air and regular exercise help keep your lungs and heart working well. You can also try to avoid breathing in particles that might irritate your lungs. Some people now wear a mask when they cycle in big cities. This helps to cut down the amount of pollution from car exhaust fumes that they breathe in. People with asthma need to be especially careful.

It is not always possible to control our environment. But there is one thing we can do to help protect our lungs. We can decide not to smoke.

Lungs & Breathing