Bob B. answered • 04/12/19
PhD in Physiology - Enthusiastic Professor!
I'm assuming you mean gas exchange in the lungs and the driving force for the movement of gas from the lungs (alveoli) into the blood is a partial pressure gradient. The pressure of oxygen in the lungs is higher than the partial pressure of oxygen in the venous blood that is moving to the lungs to become oxygenated. Therefore, oxygen will move down its pressure gradient from the lungs (~100 mm Hg) and into the venous blood (~40 mm Hg). Carbon dioxide is moves the opposite direction but for the same reason, that is, a partial pressure gradient. Message me and we can set up a review session if you need more help. Cheers!
