Model Lung

What's going on: (from http://sciencesquad.questacon.edu.au/activities/model_lung.html)

In this model, the straw acts as an airway, the balloon inside the bottle acts as a lung, the stretched balloon acts as a diaphragm and the inside of the bottle acts as a chest cavity.

When you pull down on the ‘diaphragm’ balloon, the volume inside the bottle gets bigger. This decreases the air pressure inside the bottle so it is lower than the air pressure outside the bottle. Air flows from high pressure to low pressure, so air flows into the straw and fills the ‘lung’ balloon. When a person inhales, the diaphragm contracts and makes the volume of the chest cavity bigger. Air from outside enters the airways and fills the lungs.

When you let go of the ‘diaphragm’ balloon, the volume inside the bottle gets smaller. This increases the air pressure inside the bottle so it is higher than the air pressure outside the bottle. Air flows out of the ‘lung’ balloon through the straw. When a person exhales, the diaphragm relaxes and makes the volume of the chest cavity smaller. Air leaves the lungs and flows out of the airways.

The respiratory system is vital for survival. It works closely with the circulatory system to bring oxygen into the body and to remove carbon dioxide from the body. During inhalation, air containing oxygen moves into the lungs. The oxygen moves from the alveoli of the lungs into the capillaries of the circulatory system and the circulatory system transports the oxygen to the body’s cells.

The cells use oxygen to undergo cellular respiration, a process that converts chemical energy in nutrients to adenosine triphosphate (ATP). ATP can be used to power the cells’ activities. Cellular respiration creates carbon dioxide as a waste product. When carbon dioxide mixes with water it creates carbonic acid. Because cells don’t function well in an acidic environment, it’s important to remove the carbon dioxide. The carbon dioxide moves from the cells into the capillaries and travels via the circulatory system to the lungs. At the lungs, the carbon dioxide moves from the capillaries and into the alveoli of the lungs. During exhalation, this carbon dioxide is emitted from the body.