Outline the physiological factors that affect the diffusion of oxygen and carbon 
dioxide within the lung.

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College Answer

Good answers to this question were those that included a definition of diffusion; an outline of 
Fick’s Law of Diffusion and then a further description how each of the variables in the this Law 
affect the diffusion of oxygen and carbon dioxide in the lung; and an outline of the other factors 
that affect diffusion not covered by the above. Most candidates included Fick's Law in their 
answers and at least briefly expanded on the associated variables. 
Few candidates defined the process of diffusion. The other common omissions were the 
factors that affect diffusion that aren't directly encompassed in Fick's Law, such as cardiac 
output, capillary transit time, carbonic anhydrase (conversion of HCO3 to CO2) and 
combination of oxygen with haemoglobin