Diffusion gradient for oxygen between the alveoli and the pulmonary capillaries?

The diffusion gradient for oxygen between the alveoli and the pulmonary capillaries is driven by the difference in partial pressures of oxygen (pO2) in these two compartments. In the alveoli, the pO2 is higher due to fresh air being inhaled, while in the pulmonary capillaries, the pO2 is lower because oxygen has been utilized by the body's tissues. This gradient facilitates the passive diffusion of oxygen from the alveoli into the blood, allowing for efficient gas exchange and oxygenation of the blood. The process continues until equilibrium is reached, ensuring that oxygen is delivered to tissues throughout the body.