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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
