Morphometry of Distal Airways and the Estimation of Pulmonary Gas Exchange Function

　If we run as fast as we can for a prolonged period we can burn every minute as much as five liters of oxygen to generate the energy required for muscle activity. All this O₂ disappears in the mitochondria of the muscle cells where it is consumed in the combustion of various substrates in order to make ATP, and it must be continuously replenished from the O₂ store, ambient air.