Breathing

Describe the muscular actions of the rib muscles and diaphragm during the process of inhalation and exhalation.
Explain how the movement of the ribcage and diaphragm leads to changes in chest volume and pressure.
Define lung volume and identify factors that can increase or decrease it.

It is essential that breathing continues to that oxygen is taken into the body, and carbon dioxide is removed.
This is what happens in your body when you inhale:

The muscles between your ribs contract, pulling your ribcage up and out.
The diaphragm contracts and moves down.
This increases the volume inside your chest, decreasing the pressure and allowing air to flow into your lungs.

Movement of the ribcage and diaphragm when inhaling

This is what happens in your body when you exhale:
- The muscles between your ribs relax, moving the ribcage down and in.
- The diaphragm relaxes and moves up.
- This decreases the volume inside your chest, increasing the pressure and pushing air out of your lungs.

Movement of the ribcage and diaphragm when exhaling

You can measure your lung volume by breathing out into a bottle. The air you breathe out fills the bottle, showing your lung volume.
Regular exercise can increase lung volume, as larger lungs allow more oxygen to enter the body with each breath.
Factors that can reduce lung volume include:
- Smoking, which damages lung tissue.
- Respiratory diseases like asthma.
- Aging, which reduces lung elasticity.

Inhale: To breathe air into the lungs.
Exhale: To breathe air out of the lungs.
Rib muscles: Muscles located between the ribs that help move the ribcage during breathing.
Diaphragm: A large, dome-shaped muscle located at the base of the chest cavity that is essential for breathing.
Contract: When a muscle shortens and pulls.
Relax: When a muscle lengthens and returns to its resting position.
Lung volume: The amount of air that can be held in or moved by the lungs.
Pressure: The force exerted by air; differences in pressure drive air flow into and out of the lungs.

Investigate in more detail how regular exercise can increase lung volume and improve the strength and efficiency of the respiratory muscles (rib muscles and diaphragm).
Build or investigate a simple model (such as a bell jar model) to physically demonstrate how the movement of the diaphragm and changes in chest volume and pressure cause air to move into and out of the lungs.