4 YOUR LUNGS Try to sit perfectly still Notice how your chest rises and falls That is because your lungs are working to keep you breathing Breathing is involuntary Your lungs do it without your thinking about it Lungs are baglike organs or body parts All animals that have a backbone and breathe air like you have lungs When an animal inhales breathes in air filled with Breathing is an example of an involuntary action Without the body’s involuntary actions other actions like standing smiling and taking a picture would be impossible
5 oxygen flows into the lungs The body needs a steady supply of oxygen to live When an animal exhales breathes out a different gas flows out of the lungs Other organs in the body help with breathing For example the brain sends signals to the lungs to make sure the breathing never stops Involuntary means not done on purpose Breathing is an involuntary action because the body does it automatically The left lung is smaller than the right lung This makes room for the heart to fit in between them
6 LOCATING THE LUNGS A human body has two lungs One lung is on each side of the chest They make one of the largest organs in the body Each lung has about 300 million tiny air sacs If it were possible to stretch these air sacs out and lay them flat your lungs would cover an area as large as a tennis court The left lung is a little smaller than the right lung Its smaller size makes room for If spread out an adult lung can cover half the area of a tennis court That’s a lot of lung
7 the heart which sits between them The lungs are protected by the rib cage which surrounds them The lungs sit on a muscle called a diaphragm In normal breathing the diaphragm and muscles between the ribs automatically tighten and relax This movement helps the lungs to fill with air and to empty How do different parts of the body help the lungs COMPARE AND CONTRAST Ribs protect both lungs The diagram shows the inside of one lung with the ribs cut away
