NS - Respiration II

Question 1

How does the lung affect inhalation compliance? (2)

Answer 1

1) Elastic fibres
2) Surface tension in alveoli

Question 2

What is surfactant?

Answer 2

A surface active agent in water

• Greatly reduces the surface tension of water

Question 3

Why is surfactant required in the alveolus?

Answer 3

Small alveolus would be under high pressure and would collapse
- Surfactant reduces surface tension, pressure is equalised

Question 4

What are the main 3 benefits of using surfactant?

Answer 4

1. Stabilises the alveoli
2. Reduced work in inspiration (increases compliance)
3. Keeps alveoli dry

Question 5

What is dead space in the lungs?

Answer 5

The voume of ventilated air that does not participate in gas exchange

Question 6

What is partial pressure?

Answer 6

The pressure exerted by each type of gas in a mixture

Question 7

What is Dalton’s Law?

Answer 7

Ptotal = P1 + P2 + P3
Total pressure is the sum of the partial pressures

Question 8

How can alveolar PP of O2 and CO2 change? (3)

Answer 8

1. ALVEOLAR VENTILATION RATE
2. INCREASED O2 CONSUMPTION AND CO2 PRODUCTION (EXERCISE)
3. ATMOSPHERIC pO2 AND pCO2 ALTER WITH ATMOSPHERIC PRESSURE (ALTITUDE)

Question 9

What does Fick’s law state?

Answer 9

The rate of diffusion of a substance across the unit area is proportional to the concentration gradient

Question 10

What 3 things does rate transfer from the alveolar air to the plasma depend on?

Answer 10

1) Diffusion coefficient gases in water (D)
2) Diffusion distances (T)
3) Area diffusion occurs over (A)

Question 11

What does the respiratory membrane consist of (T)? (5)

Answer 11

• Layer of fluid lining the alveolus (containing surfactant)
• Alveolar epithelium
• Epithelial basement membrane
• Capillary basement membrane
• Capillary endothelium