1. The Respiratory System (2:45)
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2. The respiratory system provides oxygen to the blood and removes carbon dioxide from the body.

3. What Happens During Respiration
The respiratory system provides oxygen to the blood and removes carbon dioxide from the body.
The continual exchange of gases in both external and internal respiration is essential for survival.

4. What Happens During Respiration
In external respiration, oxygen moves from the lungs into the blood, and carbon dioxide moves from the blood into the lungs.

5. What Happens During Respiration
In internal respiration, oxygen moves from the blood into the cells, and carbon dioxide moves from the cells into the blood.

6. How Respiration Works
The respiratory system consists of the lungs, trachea, and diaphragm.
Your lungs automatically fill with air and are emptied in a rhythmic way.

7. How Respiration Works
As you inhale, the diaphragm and the muscles between your ribs contract, expanding your chest cavity and your lungs.
Diaphragm
A muscle that separates the chest from the abdominal cavity

8. How Respiration Works
As you inhale, the pressure inside your lungs is lower than the pressure outside your body, so air flows into your lungs to equalize the pressure.

9. How Respiration Works
As you exhale, the pressure inside your lungs is higher than the pressure outside your body, so air flows out of your lungs to the outside to equalize the pressure.

10. Air moves into the lungs through the trachea.
The windpipe

11. The trachea branches out into two bronchi.
The Lungs
The trachea branches out into two bronchi.
Bronchi
The main airways that reach into each lung

12. The Lungs
A network of tubes called bronchioles branch from the bronchi.
At the end of each bronchiole are groups of microscopic structures called alveoli, thin-walled air sacs covered with capillaries where gas exchange takes place.

14. Other Respiratory Structures
The respiratory system also includes these structures in the upper airways.
Air enters and exits your body through the nose and mouth
Nose and Mouth
Air moves from the nose and mouth into the pharynx, or throat
Pharynx
Air moves from the pharynx into the trachea, or windpipe
Trachea
Larynx
Connects the throat and the trachea
Closes off the entrance to the larynx and the trachea
Epiglottis

15. Maintaining Your Respiratory Health
Caring for your lungs can prevent many respiratory disorders.
The single most important decision you can make for your respiratory health is not to smoke.

16. Maintaining Your Respiratory Health
Avoid tobacco use and exposure to secondhand smoke.  
Get regular physical activity. 
Wash your hands regularly.
Limit your exposure to pollutants in the air. 

17. Respiratory System Problems
Problems of the respiratory system can be mild, such as a cold, or serious and even life threatening.
Colds and influenza are common infections of the upper respiratory system.

18. Respiratory System Problems
An inflammation of the tissues that line the sinuses, air-filled cavities above the nasal passages and throat.
Sinusitis
An inflammation of the bronchi caused by infection or exposure to irritants such as tobacco smoke or air pollution.
Bronchitis
An inflammation of the lungs commonly caused by a bacterial or viral infection.
Pneumonia

19. Respiratory System Problems
During an asthma attack, an involuntary contraction of smooth airway muscles leads to chest tightness and breathing difficulty.
Asthma
An inflammatory condition in which the trachea, bronchi, and bronchioles become narrowed, causing difficulty breathing

20. Respiratory System Problems
Long-term treatment of asthma includes medication that reduces inflammation of the airways and avoiding substances that can trigger asthma attacks.

21. Respiratory System Problems
When a person is infected with tuberculosis, the immune system surrounds the infected area and isolates it.
Tuberculosis
A contagious bacterial infection that usually affects the lungs

22. Respiratory System Problems
A person can have inactive tuberculosis for many years and not show symptoms.
However, if the immune system is weakened, the infection can become active, causing symptoms including cough, fever, fatigue, and weight loss.

23. Respiratory System Problems
Emphysema, which is almost always caused by smoking, causes breathing difficulty, chronic cough, and permanent tissue damage.
Emphysema
A disease that progressively destroys the walls of the alveoli

24. After You Read Reviewing Facts and Vocabulary
What causes the lungs to fill with air?
The contraction of the diaphragm and the muscles between the ribs expand the chest cavity and lungs. The lower pressure inside the lungs causes air to flow in.

25. After You Read Reviewing Facts and Vocabulary
Which problems with the respiratory system can be caused by smoking?
Bronchitis and emphysema

26. After You Read Reviewing Facts and Vocabulary
How can washing your hands protect your respiratory system?
Frequently washing hands helps keep them free of bacteria and viruses that can be easily transmitted to the respiratory system by touching the nose and mouth.