Bring Science Home An inhalation activity from Science Buddies
Key Concepts Biology The body Lungs Physics Air pressure Introduction Background Air flows in via our mouth or nose. The air then follows the windpipe, which splits first into two bronchi: one for each lung. The bronchi then split into smaller and smaller tubes that have tiny air sacs at their end called alveoli. We have millions of alveoli in our lungs! These sacs have thin walls—so thin that oxygen and carbon dioxide can pass through them and enter or leave our blood. The blood transports oxygen to almost every part of the body. The blood also gives the carbon dioxide a ride back to the lungs. Lungs take up most of the space in the chest. The 12 pairs of ribs in our ribcage protect the lungs and other organs in our chest cavity, such as our heart. Relaxed breathing is a reflex; we do not have to think to breathe. During this unforced inhalation our diaphragm—the dome-shaped muscle between the chest and the abdominal cavity—flattens. This expands the chest cavity and as a result air is drawn in. During exhalation the diaphragm relaxes and the lungs naturally recoil, and air is gently pushed out. We can also breathe more forcefully. When we exercise, sing loudly or otherwise need or want more air or oxygen we can exert force to breathe more deeply. We use various muscles to increase chest volume more dramatically. In the same way as in relaxed breathing the expansion of the chest cavity draws air in so the lungs fill up. The relaxation of the chest cavity pushes air out. Muscles can also force the chest cavity to contract even further, pushing even more air out. Because the expansions and contractions are larger in this case a bigger volume of air flows in and out of our lungs, and our body gets a larger supply of oxygen or we have more air to create sound. Materials
Observations and Results When you pushed the knot in, the space inside the bottle decreased, and the balloon probably deflated. In the same way, when the diaphragm relaxes the chest cavity decreases, and air is pushed out of the lungs, and we exhale. When you pulled and pushed the knot further the balloon inflated and deflated more. This mirrors what happens when a bigger volume of air is displaced when we breathe more deeply. This dynamic works because of air pressure, a measure of how hard air presses against objects. Air pressure increases when you decrease the amount of space the air has—and decreases when you give air more space. Close a flimsy empty plastic bottle and try to compress it. It is difficult! The air inside pushes back. Open the bottle, and try to compress the bottle again. It is much easier. The air presses back with a much reduced force. Unless something blocks the movement, air will move from areas of high pressure to areas where the pressure is lower, and this is what happens when air rushes in or out of the lungs. When the chest cavity expands there is more space around your lungs. In this condition the lungs can expand, making it a low-pressure area, and air rushes in to balance out the difference in pressure. Then to breathe out the chest cavity and lungs shrink. This raises the air pressure in your lungs, and the air rushes back out. More to Explore This activity brought to you in partnership with Science Buddies Discover world-changing science. Explore our digital archive back to 1845, including articles by more than 150 Nobel Prize winners. Subscribe Now! |