| How do you workout surface: volume ratio ? | Workout out the surface area and then for volume and work out the simplest form |
| Factors that increase diffusion | Large surface
Short diffusion pathway
Maintaining a different concentration gradient |
| Inspiration | The diaphragm muscle contracts and flatten downwards .
The external intercostal muscles contract, pulling the ribs up and out. The internal intercostal muscles remain relaxed .
This increases the volume of thorax and the lungs , and stretches the elastic walled alveoli.
This decreases the pressure of air in the alveoli below atmospheric.
Air flows in from high pressure to low pressure . |
| Normal expiration | The diaphragm muscle relaxes and curve upwards . The external intercostal muscles relax , allowing the ribs to fall .
This decreases the volume of the thorax and the lungs , and allows the alveoli to shrink by elastic recoil .
This increases the pressure of air in the alveoli above atmosphere.
Air flows out from high to low pressure . |
| Structural adaptions of the alveoli | - small to increase surface area
-single layer of flattened epithelial cells for a short diffusion pathway
-maintain conc gradient |
