Breathing

A series of free Science Lessons for 7th Grade and 8th Grade, KS3 and Checkpoint Science in preparation for GCSE and IGCSE Science.

Breathing
When you inhale:

• the intercostal muscles contract, expanding the ribcage.
  
• the diaphragm contracts, pulling downwards to increase the volume of the chest.
  
• pressure inside the chest is lowered and air is sucked into the lungs.
  
  When you exhale:
  
• the intercostal muscles relax, the ribcage drops inwards and downwards.
  
• the diaphragm relaxes, moving back upwards, decreasing the volume of the chest.
  
• pressure inside the chest increases and air is forced out.

Model of a lung
This model shows how the action of the diaphragm changes the air pressure and inflates and deflates the lungs. In the real body, the ribs (represented by the plastic bottle also moves).

Investigating Vital Capacity
The vital capacity is the maximum amount of air that can be forcibly exhaled after breathing in.
You can investigate your vital capacity by exhaling into a graduated plastic bottle full of water and measuring tha volume of air that is collected.

Try the free Mathway calculator and problem solver below to practice various math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page.