DRILL_ Why Do We Breathe_ 7th grade science q1 week 4

1. Why Do We Breathe? By Jennifer Kenny Did you know that you will probably breathe in and out about 50 MILLION times in your life? Breathing means life for everyone. You have to breathe all the time. Do you know what's so amazing, though? You don't have to think about breathing. You just do it! A baby breathes about 40 times a minute. A child breathes about 30 times a minute. An active adult breathes about 25 times a minute. Finally, a resting adult breathes about 15 times a minute. You take in about one cup of air during each breath while you are resting. If you were doing something more active, though, like running, you would take in about six cups of air. Air contains oxygen. Oxygen keeps us alive. Oxygen goes to our cells and works with our food to give our body energy to keep going. We breathe out carbon dioxide. Our respiratory system is the system in the body of all the body parts used in breathing. When you breathe in, air goes through your nose and down your windpipe (or trachea). The windpipe splits into two smaller tubes called bronchi. These tubes lead into

2. your lungs. The bronchi keep branching into smaller tubes called bronchioles. Finally, they have tiny pockets of air on the end called alveoli. Oxygen from the air you breathe passes from your lungs into your blood through these alveoli. There are about 300 million alveoli in your lungs. They have very thin walls. The oxygen is then carried to your cells. The hemoglobin in your red blood cells soaks up oxygen. Carbon dioxide passes the other way from your cells to your lungs when you breathe out. Sometimes the air you breathe is filled with dust, smoke, and dirt. This could hurt your lungs. Your nose has slimy liquid called mucus. This mucus holds some of the dirt when you breathe in. When you blow your nose, you get rid of it. Your air tubes also have mucus and tiny hairs called cilia. This is how your air tubes trap the dirt to keep it away from your lungs. Coughing and sneezing can get rid of pollutants here. Cilia can be damaged, though, if a person smokes. The smoker's lungs can fill up with tar. A smoker can then become sick with cancer, chronic bronchitis, or heart disease. So, protect your respiratory system, because breathing is life.