1. The Respiratory System

2. Oxygen Oxygen is needed for most life to exist. Why?
Without oxygen, the cells in the body would not be able to release the energy in glucose for power and they would die within minutes.
This process is called “Cellular Respiration.”
Cellular Respiration: a process that happens inside a cell where oxygen is used to release chemical energy from molecules of glucose.
The waste products produced are carbon dioxide and water.

3. Oxygen cannot be stored by your body.
The respiratory system supplies the body with oxygen (O2) and removes carbon dioxide (CO2).

4. Components of the Respiratory System
The parts of the body responsible for supplying oxygen are:
nose and nasal passages
trachea
lungs (bronchi, bronchioles, alveoli)
breathing muscles—diaphragm & intercostals (muscles between ribs)
Important: The lungs are not a muscle!

5. Your nose does more than just smell things!
In the nose and nasal passages, incoming air is warmed, moistened, and cleaned of foreign particles.
Air passages are lined with mucus that traps the particles.
Interesting fact: your respiratory system produces ½ cup of mucus per day!

6. Air travels down through the windpipe, or trachea, which divides into two branches called bronchial tubes, one entering each lung.
Bronchial Tubes
Trachea

7. The bronchi branch again and again inside the lungs, similar to the branching pattern of tree roots, finally becoming hair-like tubes called terminal bronchioles.

8. Alveoli
At the end of the terminal bronchioles are microscopic bubble-like structures called alveoli.
Each lung contains 300 million alveoli!
If the surface of all the alveoli was spread out flat it would cover an area the size of a tennis court.

9. Tiny thin-walled blood vessels called capillaries surround each alveolus. Oxygen passes through the walls of the alveoli and into the capillaries and is carried throughout the body.

10. Lungs
The lungs are two football-sized spongy bags where oxygen enters the blood and carbon dioxide leaves the blood.
The lungs fill the chest cavity between the neck and the bottom of the rib cage.
Lungs contain no muscles
So how does breathing work?

11. How Breathing Works Breathing depends on:
the diaphragm that forms the floor of the chest cavity
the intercostal muscles between the ribs
Intercostals
Diaphragm

12. Breathe in! The diaphragm muscle contracts and drops down.
The ribs expand outward (intercostal muscles).
This makes the chest cavity larger.
The pressure in the chest cavity is decreased, causing air to be sucked into the lungs, causing them to expand.
This is called inhalation.

13. Breathe out!
During exhalation (breathing out), the diaphragm relaxes and moves up.
The chest cavity is made smaller.
This causes the pressure to increase and forces air full of carbon dioxide out of the lungs.
Therefore, breathing is a simple mechanical process based on pressure changes due to chest cavity size.
Video of inhalation & exhalation

14. To summarize…
When the chest cavity is made smaller, pressure increases, forcing air out of the lungs (you exhale)
When the chest cavity is made larger, pressure inside decreases, sucking air into the lungs (you inhale)
Remember, the change is chest cavity size occurs due to action of your diaphragm and intercostal (rib) muscles. Lungs cannot inhale or exhale on their own. Lungs are not a muscle!