Which of the following is true about the physiologic control of heat and moisture exchange by the body?
a. The nose, oropharynx, and hypopharynx add heat and humidity during exhalation.
b. The nose, oropharynx, and hypopharynx cool gas and reclaim water during inhala-tion.
c. The inability of the nasal mucosa to reab-sorb excessive amounts of exhaled con-densation in cold weather causes a "runny nose."
d. The mouth is more efficient at reclaiming heat and water during exhalation than is the nose.
ANS: C
A runny nose in a cold environment is caused by the inability of the nasal mucosa to reabsorb excessive amounts of exhaled gas condensed in water. The upper airways add heat and humidity to inspired gases during inhalation, and cool and reclaim water during exhalation. During exhala-tion, the mouth is much less efficient than the nose in reclaiming heat and water.
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A patient with a measured plasma HCO3– concentration of 24 mmol/L has an episode of acute hypoventilation, with the PCO2 rising from 40 to 70 mm Hg. What do you predict will happen acutely to the plasma HCO3– concentration?
a. HCO3– will remain unchanged. b. HCO3– will rise to approximately 27 to 28 mmol/L. c. HCO3– will fall to approximately 20 to 21 mmol/L. d. HCO3– will rise to approximately 54 to 55 mmol/L.