Question

When our teacher was talking about the gas exchange inside the alveoli, he mentioned the flow of air and the flow of blood was going in opposite directions so that there always would be a concentration difference.

Because of this the gas exchange between the alveolar space and capillary continues and reaches ~99%.

I could not understand how the air would always go in the same direction so I researched the topic. All resources I found state that when the air enters the alveolus there is a pressure gradient for both oxygen and carbon dioxide between the capillary and the alveolar space.

But I found nothing mentioning the opposite direction of flow for air/blood.

So does that mean gas exchange for oxygen and carbon dioxide stops when diffusion equilibrium is reached?

Answer 1

In the process of gas exchange, oxygen diffuses from the alveoli into the capillaries, while carbon dioxide diffuses in the opposite direction. This occurs due to a concentration gradient and simple diffusion.

Step-by-step explanation:

In the process of gas exchange in the alveoli, oxygen moves from the alveoli into the surrounding capillaries, while carbon dioxide moves in the opposite direction, from the capillaries into the alveoli. This gas exchange occurs by simple diffusion, meaning that gases move from areas of high concentration to areas of low concentration. Initially, there is a higher concentration of oxygen in the alveoli than in the capillaries, so oxygen diffuses into the blood. Similarly, carbon dioxide, which has a higher concentration in the capillaries, diffuses out of the blood and into the alveoli.