A small blockage in one of the pulmonary capillaries results

A small blockage in one of the pulmonary capillaries results in a ventilation-perfusion inequality. The inequality leads to _________ in the affected alveoli, which results in the homeostatic response of __________ .

a) low PCO2; local bronchoconstriction

b) low PCO2; local vasoconstriction

c) low H+; increased alveolar ventilation

d) low PO2; local vasoconstriction

e) low PO2; local bronchoconstriction

Solution

Ans D

Low pO2 and local vasoconstriction.

Normally the v/q ratio is 4/5 or 0.8 . This means litres of oxygen paas through lungs each minute and 5 litre of blood pass through lungs each minute.

Any obstruction or blockage will cause insufficient ventilation hence decreasing the partial pressure of oxygen in blood also causing local vasoconstriction