An exchange surface is in direct contact with the external environment in the
A)lungs.
B)skeletal muscles.
C)liver.
D)heart.
E)brain.

Question

Quizplus · Accepted Answer

The lungs are responsible for gas exchange between the external environment and our blood. Oxygen from the air we breathe diffuses across the walls of the air sacs in the lungs and into our bloodstream, while carbon dioxide in our bloodstream diffuses across the air sac walls and into the air we exhale. Therefore, the exchange surface in the lungs is in direct contact with the external environment.

An Exchange Surface Is in Direct Contact with the External