Ventilation

Gas exchange system

Ventilation systems move air in and out of the lungs, providing an efficient gas exchange surface in the alveoli. Ventilating the lungs is done by the relaxation or contraction of the intercostal muscles, changing the pressure of the chest cavity, so air is forced in or out of the lungs as a result of differences in pressure.  

When air moves into the lungs, it maintains a steep concentration gradient with the blood so it can diffuse continually through the alveoli. Exhaling removes carbon dioxide which maintains a steep concentration gradient so it…