3. Alveoli and Gas Exchange

Question 1

What should you do to make it as easy as possible for the oxygen molecule to diffuse?

Answer 1

Short distance - thin walls of capillary and alveolus.

Question 2

How is the diffusion gradient maintained?

Answer 2

Constant circulation of blood

Question 3

What other feature of the alveoli increase the rate of diffusion?

Answer 3

Large number of alveoli which provide a very large surface area

Question 4

How does oxygen go from alveolus to blood

Answer 4

Diffusion
Through alveolar epithelium
Through capillary endothelium

Question 5

How does Ficks law relate to alveoli

Answer 5

Large surface area- - ‘grape’ like structure of alveoli

Short diffusion distance-alveoli are 1 cell thick

Concentration gradient-continuous blood flow maintains gradient on capillary side; air in the alveoli is constantly refreshed

Question 6

Gas exchange in summary….

Answer 6

Gas exchange surfaces
Have a large surface area-to-volume ratio
Are very thin
Are partially permeable
Have a movement of internal and environmental medium (air and blood)

Capillaries are narrow
To slow down the flow of blood to allow more time for diffusion
To make sure the red blood cells are squeezed against the wall

Question 7

Why do the alveoli look different sizes?
Calculate the width of an alveoli.

Answer 7

1. When interpreting a photomicrograph of biological material it is important to remember that what you are looking at is a very thin slice of tissue. When this is cut the shape of the tissue may be altered. When taking the slice you may cut across structures in different planes. For example if you cut across a bunch of grapes some will be cut through the middle but others will be cut to the side. Not every grape (alveolus!) will be an oval.

Question 8

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.

Answer 8

Question 9

Why do mammals and birds have a high oxygen requirement?

Answer 9

The amount of oxygen that is required by mammals is high because
Mammals are large organisms with many cells
A high body temperature must be maintained

Question 10

Why do mammals and birds have a high oxygen requirement?

Answer 10

The amount of oxygen that is required by mammals is high because
Mammals are large organisms with many cells
A high body temperature must be maintained