(2) Gas exchange of O2 and CO2 between the alveoli and blood by diffusion
through the pulmonary membrane.
Transport of blood and body fluids to and from the body cells.
(4) Regulation of circulatory and ventilating systems by specific neuronal
structures in response to changes in their environment.
d. Lung Volumes Associated with Breathing. There exist certain volume
changes associated with breathing that can be accurately recorded by an instrument
called a spirometer. The tidal volume is the volume of air exchanged in normal
breathing and is approximately 500 mL. The inspiratory reserve volume is the extra
volume of air that can be inspired over and beyond normal tidal volume and is
approximately 3,100 mL. Expiratory reserve volume is the amount of air that can still be
expired forcefully, after normal tidal expiration is approximately 1,200 mL. Vital capacity
is the sum of tidal volume, inspiratory reserve volume and expiratory reserve volume.
After forceful expiration, the lungs still contain a given amount of air that is termed the
residual volume. This volume averages 1200 mL.
231. EXCHANGE OF GASES
As blood passes through the lungs, the concentration of oxygen (PO2) and the
concentration of carbon dioxide (PCO2) become nearly equal to the PO2 and the PCO2 of
the air in the lungs. That is, since the concentration of oxygen in the atmosphere is
greater than the concentration of oxygen in the blood, the oxygen moves into the blood
in an attempt to equalize the concentrations. Likewise, since the concentration of
carbon dioxide in the blood is greater than the concentration of carbon dioxide in the
atmosphere, the carbon dioxide moves from the blood to the air in an attempt to
equalize the pressure. Dalton's Law explains this partial pressure principle.
232. OXYGEN TRANSPORT
As oxygen diffuses into the pulmonary blood, it is mainly transported by the blood in
combination with hemoglobin. Although only 2.3 mL of oxygen per 100 mL of blood is
present due to the partial pressure principle, an additional 20.1 mL of oxygen per 100
mL of blood can be transported in association with hemoglobin.
233. CARBON DIOXIDE TRANSPORT
Only about 5 percent of the carbon dioxide in the blood is transported in the
dissolved state. About 95 percent of the carbon dioxide enters the red blood cells
(RBCs) where it undergoes one of two reactions.