Exchange of Gases - Outline

Description:

Alveoli are the primary sites for the exchange of gases. Exchange of gases between blood and tissues and the alveoli happen by the process of simple diffusion based on the concentration / pressure gradient.

Rate of the diffusion is affected by the solubility of gases and the thickness of the membranes.

Partial pressure is the pressure contributed by an individual gas in a mixture of gases. Partial pressure is represented by pO₂ for oxygen and pCO₂ for carbon dioxide. Solubility of carbon dioxide is 20 -25 times higher than oxygen so the amount of carbon dioxide that can diffuse through the diffusion membrane per unit difference in partial pressure is much higher than that of oxygen.

Factors determining the rate of gas exchange

• Thickness of respiratory membrane.
• Surface area of membrane.
• Diffusion coefficient of gas.
• Pressure difference across the membrane.