alleryStart learning →What oxygen partial pressures are quoted for alveolar air and for blood in the pulmonary veins?
AAbout 104 mm Hg and about 100 mm Hg
BAbout 100 mm Hg and about 104 mm Hg
CAbout 104 mm Hg and about 40 mm Hg
DAbout 40 mm Hg and about 100 mm Hg
Answer & Solution
Correct answer: A. About 104 mm Hg and about 100 mm Hg
1. Alveolar air holds an oxygen partial pressure of about 104 mm Hg.
2. Blood leaving in the pulmonary veins holds about 100 mm Hg.
3. Blood ends slightly below alveolar air rather than above it, so the second option is the reversal trap.
4. The 40 mm Hg figure belongs to blood arriving in the pulmonary capillaries, before exchange has taken place.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 22 "The Respiratory System", section 22.4 Gas Exchange_
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