How do our lungs help us breathe?
There are a number of books listed in the bibliography that have excellent illustrations. Teachers might also consider use of a purchased or homemade chart of the process of respiration.
All human beings need air to survive. Actually, we need oxygen contained in the air. While food is also a necessity, we can survive for days without it. Without air, however, we would quickly die. During the process we call respiration we breathe in air into our lungs. When we release or exhale, carbon dioxide and water vapor are released. The oxygen we take in helps to oxidize or “burn food.” Plants are the corner stone of this process. All living things depend upon food synthesized from raw materials in the leaves of green plants. Plants depend on their parts to help produce this food.
Humans and animals breathe through their lungs. As we breathe in air passes through the nasal passages above the mouth where it is warmed and filtered. The air then moves through the voice box or larynx where two tubes are found. One channels food into the stomach and the other called the windpipe goes into the lungs. When we eat or drink a flap of tissue covers the windpipe so we do not swallow food into our lungs. From there the windpipe divides into two tubes called bronchi. At the end of each bronchus tube is one of our two lungs. Within the lungs are a series of progressively smaller branches of tubes. At the end of the tiniest tube is a tiny air sac. These sacs swell like tiny balloons when we breathe air into our lungs. Surrounding these sacs are many capillaries. Oxygen breathed into the sacs pass through the sacs’ thin walls into the capillaries. Carbon dioxide and water vapor in the capillaries pass the opposite way into the air sacs. Children should remember oxygen in, carbon dioxide out.2
There are a couple of experiments that should be done here. First, we want to show that people do exhale carbon dioxide. It can be simply done by utilizing Experiment # 2 in Appendix A.3 The limewater in the experiment reacts with carbon dioxide and turns milky white and, thereby, shows the presence of carbon dioxide. Experiment #3 in Appendix A4 demonstrates that humans exhale water vapor. Children will breathe on a mirror and the mirror will fog showing the visible water vapor.