1. Mechanism of Breathing

2. DO NOW:
Label the lung with the following terms: trachea, bronchi, bronchiole, draw alveoli

3. REMEMBER
Air flows through nose or mouth and enters the pharynx (throat)
From the throat, air enters the trachea (windpipe) -Food enters the esophagus
The trachea is the pipe that brings air to the lungs

4. The trachea splits into 2 openings to the lungs called bronchi
These split into many branches in the lung called the bronchioles
At the end of each bronchiole is a structure called alveoli, or the air sacs
From the alveoli, Oxygen can diffuse into the blood.
Carbon dioxide can diffuse from the blood to the alveoli to be exhaled.

5. How does breathing work?
What happens to your chest when you inhale?
What happens to your chest when you exhale?

6. The chest cavity is the area surrounded by the ribs.
The bottom of the chest cavity is closed off by the diaphragm

8. The diaphragm is a muscle that contracts and relaxes
What happens to the size of the chest cavity when you breathe in?
What happens to the size of the chest cavity when you breathe out?

9. Do you think that breathing is caused when the diaphragm or contracts or relaxes?

10. Inhalation happens when the diaphragm contracts
Inhalation happens when the diaphragm contracts. This increases the size of the chest cavity.
The increase in the size of the chest cavity causes a change in pressure, which naturally causes air to rush into the lungs.

11. Exhalation happens when the diaphragm relaxes
Exhalation happens when the diaphragm relaxes. This decreases the size of the chest cavity.
The decrease in the size of the chest cavity causes a change in pressure, which naturally causes air to rush out of the lungs.

12. DIAPHRAGM EXPANDS DIAPHRAGM RELAXED