Body & Senses
Why do I need to breathe?
On a quiet meadow, Flauschi notices movement without taking a single step.
The short answer
Breathing takes oxygen from the air. In the lungs it enters the blood and travels to body cells, which need it for their work. Carbon dioxide returns to the lungs and is breathed out.
Two gases, two directions
1. Make room for air
When breathing in, the diaphragm contracts and moves down.
2. Exchange gases
Air reaches tiny air sacs.
3. Let air out
During quiet breathing out, breathing muscles relax.
In the middle picture an air sac is on the left and a blood vessel on the right. Red shows oxygen entering blood; blue shows carbon dioxide leaving blood for the air.
These are different gases. Brown arrows show breathing air and green shows diaphragm movement.
Organs are simplified.
An imagined Wusel scene
Puschel and Flauschi investigate
Puschel and Flauschi stand still on the meadow. Yet their chests rise and fall a little.
Flauschi“I am moving without taking a step!”
Puschel gently places his paws by his lower ribs. Puschel“Me too. Is this my secret Wusel dance?”
Flauschi“That is breathing. In people, oxygen from the air passes into the blood inside the lungs.”
They notice a few ordinary breaths. Puschel“I am glad I do not need a reminder note for every breath.” Then they look across the meadow again.
Little Wusel quiz
Which gas from inhaled air does the body need?
Choose one answer: a), b).
- a)Oxygen
- b)Only carbon dioxide
Show answer
Correct answer: a): Oxygen The body needs oxygen from the air.
Which muscle below the lungs helps us breathe?
Choose one answer: a), b).
- a)The diaphragm.
- b)The chewing muscle that moves the jaw.
Show answer
Correct answer: a): The diaphragm. The diaphragm helps us breathe together with other breathing muscles.
Word help
- cell
- A tiny living unit. Living things are made of cells.
- oxygen
- A gas in air that our bodies take in through breathing and need for their work.
- carbon dioxide
- A gas produced, among other ways, by working body cells and breathed out.
- nutrient
- A substance a living thing needs to live and grow.
Explore in more detail
Here you will find longer explanations and further details. You can explore them together.
Understand step by step
How it works – simply explained
Make room for air
When breathing in, the diaphragm contracts and moves down. It is a large muscle below the lungs. Other muscles help enlarge the chest space, and air flows in.
Exchange gases
Air reaches tiny air sacs. Oxygen crosses their thin walls into the blood. Carbon dioxide crosses from blood into the air sacs. This is gas exchange.
Let air out
During quiet breathing out, breathing muscles relax. The lungs and chest space become smaller and air flows out, carrying carbon dioxide. Your body normally manages this without you planning each breath.
Why lungs are not emptied like a bottle
A breath does not completely empty and refill the lungs like a bottle. Air remains after an ordinary breath out. The next inhalation brings in fresh air. Exhalation removes some of the air again. At air sacs, the two gases cross in opposite directions at the same time. Oxygen helps the body release energy from nutrients. Cells need this energy to work. These processes produce carbon dioxide, which blood carries back to the lungs.
References for this explanation: [1], [2], [3]
Additional specialist reference: OpenStax: Atemvorgang und Lungenvolumina
The key points again
Discovery 1
Breathing in brings air into the lungs. Air contains oxygen, among other gases.
Source: [1]
Discovery 2
In tiny air sacs – small air-filled spaces in the lungs – oxygen passes into the blood. Carbon dioxide is a gas made in the body. It moves from the blood into air in the lungs and is breathed out.
Source: [1]
Discovery 3
The diaphragm is a large muscle below the lungs. Together with other breathing muscles, it helps us breathe. Breathing is normally controlled automatically.
Source: [2]