How are ventilationperfusion ()ratios distributed throughout the ...

[lunatika]

How are ventilationperfusio n ()ratios distributed throughout the lungs in an erect position?
 
  A. High ratios predominate in the apices, and low ratios prevail in the bases.
  B. High ratios occur in the bases, and low ratios are found in the apices.
  C. High ratios prevail throughout the lungs.
  D. Low ratios predominate throughout the lungs.

Question 2

Based on the diagram shown here, which region of the pulmonary vasculature is characterized by the relationship among the pulmonary arterial, alveolar, and pulmonary venous pressures where Palveoli > Parterial > Pvenous?
 
  A. lung apex
  B. middle zone
  C. lung base
  D. This pressure relationship does not exist in the normal upright lungs.

[Laurenleakan]

Answer to Question 1

ANS: A A. Correct response: In the lungs, ratios decrease from the apex to the base. In other words, the ratios decrease along a vertical gradient from the apex to the bases. When an otherwise healthy person is mechanically ventilated, the distribution of perfusion remains unchanged. However, the overall relationship is less favorable because of the tendency of ventilation to be distributed to the nondependent lung in these patients.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.

Answer to Question 2

ANS: A
A. Correct response: The pressure relationship Palveoli > Parterial > Pvenous is located in the apical portion of the lung's pulmonary vasculature. The following pressure relationship occurs in the middle region of the pulmonary circulation: Parterial > Palveoli > Pvenous. The third possible relationship among these three pressures is found in the gravity dependent region (bases) of the upright lungs: Parterial > Pvenous > Palveoli.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.

[lunatika]

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