British Sign Language Glossaries of Curriculum Terms

BSL Biology Glossary - gas exchange - Definition

There are two different parts of gas exchange.

The first happens in the lungs. In the lungs there are branching bronchi, or tubes, which go down to many smaller bronchioles. At the end of these small tubes are tiny air sacs. You can see them all round the lungs. The air sacs have a protective membrane round them. The blood which feeds the lungs comes in tiny capillaries. The capillaries form a membrane round the outside of the air sac. As air comes into the lungs, the blood flows through the capillaries. Oxygen comes down from the air into the lungs and the bronchioles. The oxygen passes through the membrane into the bloodstream and becomes attached to the red blood cells. So that is one part of the gas exchange.

Now the oxygen (O₂), a gas, is in the bloodstream and flows round the body. It travels all over the body: to the skin, muscles, and the brain, for example. When the red blood cells arrive at the organ, the second part of the gas exchange happens. The oxygen is released to give energy to the organ. Now CO₂ comes back from the organ into the bloodstream in exchange for the oxygen, and continues flowing round the body. This is called respiration. The blood with CO₂ comes back into the heart.

So you can see there are two gas exchanges: first O₂ comes into the blood, then CO₂ takes its place. This process continually repeats itself.