qqq - honey91

[ArchivalUser]

Gas exchange in the lungs occurs in the alveoli. There are two components to this exchange, diffusion and perfusion. Either of these components can limit the exchange of oxygen from the air into the bloodstream. Which of the following describes perfusion limited exchange?

A. It is illustrated by CO and O2 concentrations during strenuous exercise

B. It is illustrated by gas equilibrating early along the length of the pulmonary capillary

C. It is illustrated by gases other than N20 and CO2 under healthy resting conditions

D. It is illustrated by the gas partial pressure difference being maintained between alveolar air and pulmonary capillary blood.

E. It is illustrated in disease states such as fibrosis and emphysema

F. It is not affected by change in blood flow

[ArchivalUser]

b b as gases are 02 ;co2;n2o

[ArchivalUser]

A-DEPEND ON BLOOD FLOW

[ArchivalUser]

B. It is illustrated by gas equilibrating early along the length of the pulmonary capillary

[ArchivalUser]

correct answer is B.

In perfusion-limited exchange, gas equilibrates early along the length of the pulmonary capillary, because it is not a problem with gas diffusion.

Answer A is incorrect. Diffusion-limited exchange is illustrated by CO and O2 during strenuous exercise

Answer C is incorrect. Perfusion-limited exchange is illustrated by N20 and CO2 under normal conditions, along with O2 under normal conditions.

Answer D is incorrect. The partial pressure of the gas in the pulmonary capillary blood becomes equal to the partial pressure in the alveolar air. It is maintained in diffusion-limited exchange.

Answer E is incorrect. Diffusion-limited exchange is illustrated in disease states such as fibrosis and emphysema, because it’s the gas, not the blood flow, that is the problem.

Answer F is incorrect. Perfusion-limited exchange is increased only if blood flow increases, and it decreases when blood flow decreases