| |
partial pressure
the pressure exerted by each of the constituents of a mixture of gases, such as in air or blood. The word partial refers to the part that is a particular gas in relation to the whole mixture.The partial pressure of oxygen in blood (Po21) reflects the number of oxygen molecules striking the surface of a membrane at any given point. Across the alveolar-capillary membrane in the lungs, for example, there may be a difference in the partial pressure being exerted by oxygen molecules on the alveolar
side and that being exerted by oxygen striking the same point from the opposite side. When the partial pressure of oxygen
in the alveoli is greater than that in the blood, oxygen molecules move across the membrane in the direction of the blood.
The same is true in regard to carbon dioxide. Carbon dioxide most often moves across the alveolar-capillary membrane from the blood to the lungs, because its partial pressure in the blood (Pco2) is greater than that in the alveoli.
Copyright 2007. An Elsevier publication. All rights reserved.
Click here for important legal information about Dorland's Medical Dictionary.
|
