Question

Why can't gas exchange occur in the bronchus?

A. There are no capillaries in the bronchus

B. The walls are too thick

C. The bronchus comprises dead tissue

D. There is no partial pressure gradient between the air in the bronchus and the blood in the capillaries

Answer 1

ANSWER

B. The walls are too thick.

EXPLANATION

For effective gaseous exchange to take place, the thickness of the wall should be thin. For alveoli, the wall is so thin (single cell thick) that the exchange of gas will be effective.

The adaptations of alveoli which help in gas exchange are:

1. Alveoli are one cell thick.

2.It has good blood supply.

3.It is moist to allow dissolution of oxygen to promote exchange of gas.

4.It has increased surface area for gaseous exchange.

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