Breathing

This lesson covers: 

1. How we breathe in and out
2. The bell jar model
3. Measuring lung volume

Mechanisms of breathing in and out

Our ribs and diaphragm help us breathe.

Breathing in happens when:

• The diaphragm contracts and moves down, increasing the volume in our chest.
• The ribcage moves up and out, helping make even more space.
• This makes the pressure inside the chest decrease and air comes rushing into our lungs.

Breathing out happens when:

• The diaphragm relaxes and moves up decreasing volume in our chest.
• The ribcage moves down and in, making less space in our chest.
• This increases the pressure inside the chest and air gets pushed out of our lungs.

The bell jar model

The bell jar model is a simple way to see how breathing happens.

Steps in the bell jar breathing model:

1. Pulling down the rubber sheet is like the diaphragm moving down . This creates more space inside the bell jar.
2. The increase in space lowers the pressure inside the bell jar.
3. The lower pressure causes air to rush into the balloons, making them expand.
4. Letting go of the rubber sheet reduces the space inside the bell jar, and is similar to our diaphragm moving up.
5. Less space causes the pressure to increase, pushing air out of the balloons, similar to how air is pushed out of our lungs.

Measuring lung volumes

Lung volume is about how much air we can breathe in or out in one go.

• Lung volume is different for everyone. Your height and health can change how much air your lungs can hold.
• We can measure lung volume with a tool called a spirometer, which records how much air you breathe in and out.
• The spirometer shows us this information in a chart called a spirogram.