Alveolar Gas Exchange (W1)

Question 1

LO’s

Answer 1

1. Describe why the composition of alveolar gas is relatively constant.
2. Describe the diffusion steps across the pulmonary blood gas barrier.
3. Describe the gas pressure gradients across the blood-gas barrier, and the relative velocities of oxygen and carbon dioxide transfer.
4. Describe how hypoventilation and venous admixture (Right-Left shunt) affect gas exchange.

Question 2

Regional Variation in Alveolar Size

Answer 2

• The lungs are stretched by gravity. The alveoli at the top (apex) of the lung are more open, than those at the bottom (base) which are more compressed.
• The change in volume of the alveoli at the bottom will therefore be greatest. So ventilation is actually greatest at the bottom of the lungs.

Question 3

Obstructive/ Restrictive Lung Disease

Answer 3

• Obstructive: lungs more full of air.
• Restrictive: lungs almost completely empty of lungs.
• draw each diagram to understand

Question 4

What are the barriers in gas transfer between alveoli and blood?

Answer 4

1. Alveolar epithelium
2. Capillary endothelium
3. Interstitium (sometimes absent)

Question 5

What factors aid gas exchange in alveoli?

Answer 5

• Huge surface area
• Thin barrier