Because this factor normally varies, the most important variable that influences the diffusion of respiratory gases is the concentrationgradient.The air in the lungs has a higher concentration of oxygen than that of oxygen-depleted blood and a lower concentration of carbon dioxide. This concentration gradient allows for gasexchange during respiration.
Gas exchange during respiration occurs primarily through diffusion. Diffusion is a process in which transport is driven by a concentration gradient. Gas molecules move from a region of higher concentration to a region of low concentration. Blood that is low in oxygen concentration and high in carbon dioxide concentration undergoes gas exchange with air in the lungs.
Ventilation maintains concentrationgradients of oxygen and carbon dioxide between the air in the alveoli and blood flowing in adjacent capillaries.
