Our lungs are contained in our chest cavity (thorax).
Lung Ventilation
Wrapped around the lungs are the ribs.
The ribs expand upwards and outwards while inhaling and contract downwards while exhaling.
The Diaphragm is another extremely important muscle in breathing. It is a thin sheet of muscle and tendon which separates the abdominal cavity from the chest cavity.
As we inhale, the Diaphragm contracts downwards pulling air in. As the Diaphragm relaxes it pushes air out of the lungs.
This is shown by the yellow line in the animation to the left.
This is referred to as a ‘suction pump’ mechanism.
When we breath in, it requires energy, because we are contracting the diaphragm.
Exhalation, however, is normally a passive process, because it a result of the elastic recoil of the thorax.
When we forcefully exhale it involves active compression of the rib cage.
The volume of air we breath in and out each breath is called the tidal volume. Depending on your oxygen needs, the tidal volume varies.
If you have just finished exercising then its higher, if your sitting playing PS4 its lower.
The graph to the left shows the volume of air inhaled and exhaled as exercise increases.
What you may have noticed is that air comes in the same way it goes out, and not all the air that is in the lungs leaves before another breath is taken.
This means there is ‘stale’ air left in the airways.
This isn’t necessarily a bad thing thou, the left over air prevents the alveoli from collapsing in on themselves.
