1. How Does Your Body Take In Oxygen? Lesson 1

2. Respiratory System When you breathe in your respiratory system brings air containing oxygen into your body. The respiratory system includes the nose, nasal cavity, pharynx, larynx, trachea, bronchial tubes, lungs, and alveoli. As your cells work, they make a gas called carbon dioxide. This gas leaves your body when you breathe out.

3. Nose The nose has the job of getting air ready for your lungs. The lining of your nose produces a thick, sticky liquid called mucus. Tiny hairs in your nasal passages, bronchi, and trachea called cilia help to clean the air of dust and dirt particles.

4. Inside Your Lungs The process of breathing in is called inhaling. The exchange of oxygen for carbon dioxide in the lungs takes place in air sacs called alveoli. The process of breathing out is called exhaling.

5. How Does Your Body Use Oxygen? Lesson 2

6. Capillaries Capillaries are tiny blood vessels with very thin walls through which oxygen and nutrients can pass. As red blood cells move through a capillary, they release their oxygen to body cells outside of the capillary.

7. Red Blood Cells When red blood cells are carrying oxygen, they are bright red. After red blood cells give up their oxygen, they become dark, dull, and purplish.

8. Using Oxygen to Release Energy Nutrients are carried by plasma to the body cells. Many nutrients are simple kinds of sugar. Cells use oxygen to break the sugar down into carbon dioxide and water. This releases energy. Sugar + Oxygen carbon dioxide + water + energy

9. Energy The body needs more energy when you are very active, so more oxygen is needed by the cells. You can get more oxygen with each breath when you breathe faster and when you breathe through your mouth.