1Why we need gas exchange
Every cell needs oxygen for respiration, and makes carbon dioxide that must be removed. Your gas exchange system swaps these gases between your blood and the air.
gas exchangeoxygencarbon dioxide
Lesson 7.1 notes
The gas exchange system
Follow air from your nose down to the alveoli, see how the alveoli are built for swapping gases, and how your airways keep themselves clean.
2The way in
Air goes in through your nose or mouth and down the trachea. This splits into two bronchi, which branch into narrower and narrower bronchioles. They end in tiny air sacs: the alveoli.
tracheabronchibronchiolesalveoli
3Inside your chest
The lungs fill most of your chest, with the heart between them. The ribs protect them. The intercostal muscles between the ribs and the diaphragm below do the work of breathing.
ribsintercostal musclesdiaphragm
4Down to the alveoli
Each bronchiole ends in a bunch of alveoli, wrapped in tiny blood vessels called capillaries. Oxygen passes from the air in an alveolus into the blood in a capillary.
alveolicapillaries
5Built for gas exchange
The alveoli give a huge surface area. Their walls are only one cell thick, they are lined with moisture, and lots of capillaries carry oxygen away, so gases diffuse quickly.
surface areadiffuse
6Keeping the trachea open
Rings of cartilage hold the trachea open, so it doesn't squash flat as you breathe in. Each ring is C-shaped, with the gap at the back, next to the oesophagus.
cartilage
7Keeping the airways clean
Cells lining the airways make sticky mucus, which traps dust and microbes. Tiny hairs called cilia sweep the mucus up to the throat, where it is swallowed.
mucuscilia
Explore: Follow a breath
Send a breath of air down into the lungs. Stop at each part to see it close up and find out what it does.
Common mistake: Breathing isn't respiration
Breathing moves air in and out of your lungs. Respiration is a reaction in every cell that releases energy from glucose. Breathing supplies the oxygen that respiration uses.
Remember
- Air goes in through the nose or mouth, down the trachea, into the bronchi and bronchioles, and ends in the alveoli.
- Alveoli have a huge surface area, walls one cell thick, a moist lining and lots of capillaries, so gases diffuse quickly.
- Rings of cartilage hold the trachea open. Mucus traps dust and microbes, and cilia sweep it up to the throat.
Going further at GCSE