Earth Physiology
As you probably know, all the actions and movements of your body (and
even your ability to think) depend on the delivery of oxygen and
nutrients to the cells in your body on a constant basis. The heart is the
main pump that forces the blood through the bl
ood vessels of the body. The blood vessels form a closed system of
"highways" that transport blood and allow the exchange of gases,
nutrients, and wastes between the blood and the body cells. An estimated
62,000 miles of blood vessels throughout the body
of an adult ensure that a continuous supply of nutrients and oxygen
reaches each of the trillions of living cells and that waste products are
carried away. The blood cells, specifically the red blood cells, serve as
the "vehicles" that travel the blood-vessel highway to deliver oxygen
(O2) and to pick up the carbon dioxide (CO2) from
each cell. The lung is the "gas station," where the red blood cells drop
off the CO2 and refuel with O2 to continue their
journey among the cells. In this section, we will first examine the
structure and function of the heart and the circulation. We will then
build our story to include how the exchange of gases takes place between
the blood and the lungs.
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