Gas Exchange

Question 1

What does Fick’s Law tell us?

Answer 1

• rate of diffusion is directly proportional to the area of the diffusion surface
• rate of diffusion is directly proportional to the size of the concentration gradient.
• the rate of diffusion is inversely proportional to the thickness of the surface over which diffusion takes place.

Question 2

what properties must a gas exchange surface have?

Answer 2

• large SA
• difference in conc. between the alveoli and the blood must be kept as high as possible
• thin walls, short diffusion distance

Question 3

how is a large SA achieved in mammalian lungs?

Answer 3

• millions of alveoli and many capillaries covering the alveoli

Question 4

how is the difference in conc. between the alveoli and the blood kept as high as possible in mammalian lungs?

Answer 4

• breathing maintains a difference in gas concentrations

- blood flow maintains a difference in gas concentrations

Question 5

how is a short diff. dist. achieved in mammalian lungs?

Answer 5

• walls of capillaries are only one cell thick
• walls of alveoli are only one cell thick
• the cells forming the walls of the alveoli and capillaries are flattened.

Question 6

how does cystic fibrosis make gas exchange less efficient?

Answer 6

• thick sticky mucus means that their cilia find it difficult to move, thick sticky mucus gets accumulated in their airways - reducing flow of air into alveoli - conc. grad. for gases is reduced.
• mucus can completely block some of the airways, preventing movement of air into the alveoli beyond the blockage - reduces surface area for gas exchange.