HK 2810 Lecture 2: Physiology Lying Down vs Standing Pleural Pressures
19 Oct 2015
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A thorough explanation from a ta this has been used for 3 years in a row on the final! If we look at the graph for the alveoli at the bottom of the lung, its telling us that at -2mmhg, the alveoli don"t have very much volume of air in them and therefore aren"t very expanded. Therefore they have a great potential to take in the air from each breath than do the alveoli at the top of the lung. For that reason, we get the uneven distribution of ventilation when we are standing up. Basically, we can relate ppl to stretch on the lung (ie how expanded the alveoli are) and this stretch is then directly associated with volume within the alveoli. So you are correct with your statement of p1-p2and here is a bit of a complicated explanation for that: the pleural pressure is negative and pulls open the alveoli.
