What is the primary factor that maintains the pressure gradient ...

[Mimi]

What is the primary factor that maintains the pressure gradient that drives O2 from the capillaries into the interstitial spaces and into the cells?
 
  a. Bohr effect on the RBC
  b. Cellular consumption of O2
  c. Haldane effect on the RBC
  d. Increased carbon dioxide in blood de-creasing Hb affinity for O2

Question 2

Breathing room air, a normal PAO2  PaO2 of 5 to 10 mm Hg exists due to which of the follow-ing?
 
  1. Anatomical shunts in the pulmonary and cardiac circulations
  2. Normal limitations to O2 diffusion in the lung
  3. Regional differences in pulmonary ventilation and blood flow
  a. 1 and 3 only
  b. 2 and 4 only
  c. 1, 2, and 3
  d. 1 and 2 only

[Jayson]

Answer to Question 1

ANS: B
As cellular metabolism depletes its O2, the intracellular PO2 drops below that of the blood enter-ing the tissue capillary. This provides the diffusion gradient by which O2 diffuses from the tissue capillary blood (PO2 = 100 mm Hg) to the cells (PO2 < 40 mm Hg).

Answer to Question 2

ANS: A
Two factors account for the normal PAO2  PaO2: (1) right-to-left shunts in the pulmonary and cardiac circulation and (2) regional differences in pulmonary ventilation and blood flow.