1. Alveolar Gas Exchange
Chapter 19.5

2. Microscopic air sac clusters at the distal ends of the finest respiratory tubes (alveolar ducts)
Alveoli
Sites of the vital process of gas exchange between the air and the blood
Alveolus - tiny space within a thin wall that separates it from adjacent alveoli (SHOW ON DIAGRAM)
Megan

3. Alveolar Pores Alveolar Macrophages
Tiny openings in the walls of some alveoli
may permit air to pass from one alveolus to another
Phagocytic cells in the alveoli and pores that phagocytize airborne agents
Job = clean the alveoli
Megan

4. Megan

5. Respiratory Membrane Fill in Diagram A on Page 2 of Your Packet
Macey

6. Respiratory Membrane Wall of Alveolus
Made up of cells that secrete pulmonary surfactant
Bulk of the wall consists of a layer of simple squamous epithelium
Alveolus
Each alveolus is associated with a dense network of capillaries.
Alveolar Capillary Membrane
Two thicknesses of epithelial cells and basement membranes separate the air in an alveolus and the blood in a capillary.
Layers = respiratory membrane (alveolar capillary membrane)
Gas exchange occurs through these layers between the alveolar air and the blood.
Macey

7. Macey

8. Diffusion Through the Respiratory Membrane
Solutes
Diffuse from higher concentration to lower concentration
Determine the direction of solute = must know the concentration gradient
Dissolved Gases
Partial pressure gradients
A gas will diffuse from an area of higher partial pressure to lower partial pressure.
When a mixture of gases dissolves in blood, the concentration of each dissolved gas is proportional to its partial pressure.
Ally

9. This happens not just inside the respiratory system!
Gas Diffusion
Each gas diffuses between blood and its surroundings from areas of higher partial pressure to areas of lower partial pressure until the partial pressures in the two regions reach equilibrium.
This happens not just inside the respiratory system!
Example: PCO2 of blood entering the pulmonary capillaries is 45 mm Hg, BUT the PCO2 in alveolar air is 40 mm Hg.
Carbon dioxide diffusion = blood alveolar air (higher to lower)
Increased Diffusion
More surface area
Shorter distance
Greater solubility of gases
Steeper partial pressure gradient
For example, the PCO2 of blood entering the pulmonary capillaries is 45 mm Hg., but the PCO2 in alveolar air is 40 mm Hg. Carbon dioxide diffuses from blood since the partial pressure is higher, into the alveolar air, where partial pressure is lower.
Ally

10. Ally

11. Because of this, breath analysis can reveal alcohol in the blood or acetone can be smelled on the breath of a person who has untreated diabetes mellitus.
Extra Information
The respiratory membrane is very thin, and soluble chemicals other than carbon dioxide may diffuse into alveolar air and be exhaled.
Ally

12. These conditions may require increased PO2 treatment.
Pneumonia = inflammation and lots of unnecessary fluid in alveoli
Emphysema = damaged alveoli
Megan

13. Disorders that Impair Gas Exchange
Pneumonia
Alveolar linings swell with edema & are abnormally permeable
Allow fluids and WBC’s to accumulate in the air sacs
Surface area available for gas exchange diminishes
Breathing is difficult
Tuberculosis
Caused by bacterium Mycobacterium tuberculosis
Fibrous connective tissue develops around the sites of infection
Form structures called tubercles
Atelectasis
Collapse of a lung, or some part of it
Collapse of the blood vessels that supply the affected region as well
Tuberculosis: by walling off the bacteria, the tubercules help stop their spread.
Megan

14. Megan
TUBERCULOSIS

15. Megan

16. Macey

17. Electricity = Blood Low in Oxygen but High in Carbon Dioxide
Lightbulb = Alveoli
Electricity = Blood Low in Oxygen but High in Carbon Dioxide
Light = Blood Low in Carbon Dioxide but High in Oxygen
Magnetic Field = Air moving in and out of alveolus/Carbon Dioxide and Oxygen diffusing into the blood
Heat = oxygen is transported around the body
Power = Carbon dioxide diffusing from blood to be exhaled
Inside of lightbulb = gas-filled air space
Macey