The relationship between arterial perfusion and alveolar gas pressure at the base of the lungs is best described as:
A)alveolar gas pressure exceeds arterial perfusion pressure.
B)arterial perfusion pressure and alveolar gas pressure are less than at the apex.
C)arterial perfusion pressure exceeds alveolar gas pressure.
D)alveolar gas pressure and arterial perfusion pressure are equal.

Question

Quizplus · Accepted Answer

Zone I is where alveolar pressure exceeds pulmonary arterial and venous pressures. The capillary bed collapses, and normal blood flow ceases. Normally zone I is a very small part of the lung at the apex. Zone II is the portion where alveolar pressure is greater than venous pressure but not greater than arterial pressure.

The Relationship Between Arterial Perfusion and Alveolar Gas Pressure at the Base