The air we breathe is made up of several gases. Oxygen is the most important for keeping us alive because body cells need it for energy and growth. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also enabling the body to get rid of carbon dioxide in the air breathed out. The respiratory system include the nose, pharynx, larynx, trachea, bronchi and lungs. The respiratory system does two very important things: it brings oxygen into our bodies, which we need for our cells to live and function properly; and it helps us get rid of carbon dioxide, which is a waste product of cellular function. Respiration (breathing) is important because it produces energy that is essential for the normal functioning of the body. Respiration provides cells with oxygen and expels toxic carbon dioxide. The job of your lungs in this system is to provide these processes with oxygen and to get rid of the waste gas, carbon dioxide. Hence, your brain constantly gets signals from your body which detect the amount of oxygen and carbon dioxide in your blood.
A carcinogen is another way of describing a substance that can cause cancer, while a biopsy is a type of operation that examines a person's tissue to see if they have a certain disease. Hope this helps!
