VPB 121: Veterinary Physiology - II (2+1)

ALVEOLAR GAS EXCHANGE

• Usually, gas pressure is considered in terms of ­ total pressure, regardless of whether it is a single gas or a mixture of gases. However each gas in the mixture separately contributes to the total pressure.
• It is defined as the pres­sure exerted by a particular gas in a mixture of gases. The sum of the partial pressures of the gases within a mixture equals the total pressure.
• Because oxygen is consumed and carbondioxide is produced by cells, the venous blood will have a high PCO₂ and a lower PO₂ and vice-versa for arterial blood.
• A more active location would consume more O₂ and produce more CO₂ than less active locations. Because of these differ­ences, the jugular vein blood may not be rep­resentative of whole body venous blood (i.e., blood from the right atrium).
• Gases diffuse from an area of their higher concentration to an area of their lower concentration.
• Two gas laws are applicable to gas exchange .
• Dalton's law explains how gases move by diffusion based on pres­sure differences while Henry's law describes the diffusion of gas based on its solubility.