Two major functions of gaseous exchange are:
- to fill blood with oxygen to be transported to the working muscles.
- to remove carbon dioxide and waste products produced by metabolic process by the working muscles.
Movement of gasses in oposite directions between blood and lungs.
Each gas within a mixture of gasses exerts pressure which is equal to to its percentage within that mixture (partial pressure). The partial pressure of oxygen within the alveoli is much higher than in the the surrounding capillaries and causes oxygen to move from the alveoli into the blood, this is relevant to carbon dioxide which moves in the opposite direction.