Does carbon dioxide move from the blood to the alveoli or from the alveoli to the blood and Why does it move in this direction (use it's partial pressures)?

How does carbon dioxide exit the bloodstream at its final destination? Why does it move in the direction that it does across the alveolar surface?   When you feel a pulse, you’re feeling your radial artery expand.  What is causing your artery to expand like this?  The veins in your arms and legs have one way valves.  Explain why these valves are necessary for returning venous blood to the heart.

Does carbon dioxide move from the blood to the tissue cells or from the tissue cells to the blood and Why does it move in this direction (use it's partial pressures)?

1) when we exhale does the air push against the walls of the respiratory conducting division or pull in ?Is exhalation an active or a passive process? which tissue normally prevents the trachea and bronchial trees from collapsing under the negative pressure of inhalation? Why don’t bronchioles needs support? Which muscles are responsible for controlling inhalation?