Respiration requires oxygen as a substrate and produces
carbon dioxide. That means we need to get oxygen into the
body and carbon dioxide out.
The main part of the human gas exchange system is the
lungs, which moves air in and of the body.
Air enters the lungs via the trachea (wind pipe), which then
divide into bronchus and further divide into bronchioles in the
lungs. At the end of the bronchioles are alveoli, which are small
air sacs where the gas exchange occurs.
A key point to remember when thinking about ventilation is that air moves from high pressure to low pressure. Pressure is directly related to volume. So when volume increases pressure and decreases and vice versa
During inhalation air moves in. For this to occur the pressure
inside the lungs needs to be lower than outside.
To ensure the pressure in the lungs is lower, the diaphragm
contracts and flattens and therefore increases the volume in