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Human Performance

2.3.3 Oxygen absorption

The figure below shows how oxygenated blood is transported to all organs,

where it is used in metabolism.

Carbon dioxide-rich blood is then

returned to the heart and lungs.

The small circulation, the pulmonary

circulation, transports blood from the

heart to the lungs, where the red blood

cells are emptied of CO2, which we

exhale.

We then inhale O2, which the lungs fill

with, and the oxygen is then carried to

the heart and from there, through the

systemic circulation, to all the cells of the
body.

From the lungs, we exhale CO2 while inhaling O2, which then re-enters the

circulation.

We do not have a "buffer system" or a store of oxygen and thus live almost from

breath to breath.

When we exert ourselves and use more energy, the need for oxygen increases.

The respiratory center measures the CO2 and oxygen levels in the blood and

adjusts the breathing rate according to the physical need.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 137