1. Respiratory System Alveolar Gas Exchanges

2. Alveoli Remember, alveoli are microscopic air sacs that are located in clusters at the ends of the alveolar ducts Where gas exchange takes place

3. Alveoli Each alveolus consists of a small space surrounded by a thin wall – Tiny openings called alveolar pores in the walls of some alveoli permit air to move from one alveolus to another

4. Alveoli Alveolar macrophages – Phagocytic cells located in the alveoli and alveolar pores – Destroy airborne agent such as bacteria (clean the alveoli)

5. Alveoli Structure of the alveolar wall – Part of the wall is made up of cells that secrete surfactant – Majority of the wall consists of the respiratory membrane through which gas exchange occurs between the alveolar air and the blood (See your book description of the types of cells that make up this membrane)

6. Alveoli

7. Diffusion of gases through the respiratory membrane: – Gases (CO 2 and O 2 ) diffuse across the membrane from areas of higher partial pressure to areas of lower partial pressure

8. Alveoli Diffusion of gases through the respiratory membrane: – Because the respiratory membrane is so thin other soluble gases besides O 2 and CO 2 (such as alcohol in the blood) can diffuse across the membrane and be detected in exhaled air

9. Alveoli Factors affecting diffusion across the respiratory membrane – Diffusion is increased by: Greater surface area, shorter distance, greater solubility of gases, and a steeper partial pressure gradient