Section XI. EXCHANGE AND TRANSPORTATION OF GASES: ARTIFICIAL
7-40. EXCHANGE AND TRANSPORTATION OF GASES
a. Gases Involved. Oxygen and carbon dioxide are the primary gases involved
in respiration. Under special circumstances, nitrogen may also be of concern.
b. Pressure Gradients. A gas moves from an area where its pressure is
greater to an area where its pressure is less. Thus, the movement of gases depends
upon such pressure gradients.
c. External Respiration. At the alveoli, gases are exchanged between the air
inside and the blood in the adjacent capillaries.
d. Internal Respiration. Within the body, gases are exchanged between the
blood of the capillaries and the individual cells of the body.
e. Transportation of Gases. The gases are transported (Figure 7-5) between
the alveoli and the individual cells by the cardiovascular system.
(1) Some of the gases are dissolved directly in the plasma of the blood.
(2) However, in humans, the greater percentage of the gases is carried
within the substance of the RBCs (red blood cells, erythrocytes). The RBC, found in
great numbers in the blood, is specially constructed for transporting the gases.
Hemoglobin, a substance found within RBCs, has a great affinity for oxygen. Yet, the
hemoglobin can readily give up the oxygen wherever it is needed.