Fig.: A diagram of a section of an alveolus with a pulmonary capillary
𝗘𝗫𝗖𝗛𝗔𝗡𝗚𝗘 𝗢𝗙 𝗚𝗔𝗦𝗘𝗦
Alveoli are the primary sites of exchange of gases.
Gaseous Exchange in Lungs
● At alveoli level, gaseous exchange occur through respiratory membrane (diffusion membrane) which is 0.2 mm thick (total thickness is much less than a mm).
● 𝗜𝘁 𝗰𝗼𝗻𝘀𝗶𝘀𝘁 𝗼𝗳 𝘁𝗵𝗿𝗲𝗲 𝗹𝗮𝘆𝗲𝗿𝘀:
(i) Alveolar epithelium (thin squamous epithelium)
(ii) Basement substance in between them (composed of a thin basement membrane supporting the squamous epithelium and the basement membrane surrounding the single layer endothelial cells of capillaries)
(iii) Endothelium of alveolar blood capillaries
● Exchange of gases also occur between blood and tissues.
● O2 and CO2 are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient
● Pressure contributed by an individual gas in a mixture of gases is called partial pressure and is represented as pO2 for oxygen and pCO2 for carbon dioxide.
𝗘𝗫𝗖𝗛𝗔𝗡𝗚𝗘 𝗢𝗙 𝗚𝗔𝗦𝗘𝗦
Alveoli are the primary sites of exchange of gases.
Gaseous Exchange in Lungs
● At alveoli level, gaseous exchange occur through respiratory membrane (diffusion membrane) which is 0.2 mm thick (total thickness is much less than a mm).
● 𝗜𝘁 𝗰𝗼𝗻𝘀𝗶𝘀𝘁 𝗼𝗳 𝘁𝗵𝗿𝗲𝗲 𝗹𝗮𝘆𝗲𝗿𝘀:
(i) Alveolar epithelium (thin squamous epithelium)
(ii) Basement substance in between them (composed of a thin basement membrane supporting the squamous epithelium and the basement membrane surrounding the single layer endothelial cells of capillaries)
(iii) Endothelium of alveolar blood capillaries
● Exchange of gases also occur between blood and tissues.
● O2 and CO2 are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient
● Pressure contributed by an individual gas in a mixture of gases is called partial pressure and is represented as pO2 for oxygen and pCO2 for carbon dioxide.