3. The mechanics of respiration
Inhalation
Breathing is accomplished with the aid of the diaphragm and the muscles of the chest wall.
During inspiration (or inhalation):
- the diaphragm contracts and descends,
While at the smae time ...
- the muscles around the ribs contract to raise the ribs.
As a result of these changes the volume of the chest cavity increases. This causes air to be drawn into the lungs via the nose, pharynx, larynx, trachea and bronchi.
Exhalation In the process of expiration (or exhalation), carbon dioxide is forced out of the lungs, through the bronchi, trachea, larynx, pharynx and nose, into the environment.
Usually, no muscular effort is required for breathing out. Expiration is simply due to the elastic lungs returning to their original size and shape - rather like a rubber balloon.