Life support - Breathing

Lungs are perfect for absorbing gases:

• They have a big inside surface area
• They're moist
• They have good blood supply.

1) Some of the oxygen in the inhaled air passes into the blood stream to be used in respiration.

2) Carbon dioxide is a waste product of respiration. In the lungs it passes out of the blood and is then breathed out.

The Bell Jar demonstration shows us what's going on when you breathe:

• First you pull the rubber sheet down - like it's your diaphragm.
• This increases the volume inside the bell jar.
• Air rushes in to fill the extra volume, - this is breathing in.
• Let go of the plastic sheet - this is like relaxing your diaphragm.
• The volume in the jar gets smaller, so air rushes out.

1) The chest cavity is just like a bell jar.

2) The diaphragm moves down and the ribs move up. This increases its volume so air rushes in.

3) When the diaphragm moves up and the ribs move down air rushes out.