Without your respiratory system, you wouldn't be able to breathe, and your heart wouldn't pump. When you take a breath, it goes down to your lungs, and into your alveoli. Oxygen then moves from your alveoli, into capillaries in your blood. There are 300 million alveoli's attached at the end of your bronchi.

For your respiratory system to work properly, you have to take proper care of it. Smoking is bad for your lungs, for you are just breathing in smoke, and may cause lung cancer. Lung cancer is a disease that causes you to suffocate eventually. Asthma isn't so great to get, but you don't get it by taking bad care of yourself. You can get it even if you're the healthiest person in the world. Asthma is when you have airway constriction. Airway constriction is caused by your bronchi's to narrow and swell up, I guess you'd say. Asthma attacks are caused by pollen getting into you. There are medicines for asthma, unless it is too serious.