The Lungs

Question 1

Describe the process of gas exchange in the lungs.

Answer 1

Upon inhaling, the alveoli fill with oxygen.
The blood in the capillaries surrounding the alveoli is deoxygenated.
So, the oxygen in the alveoli diffuses down the concentration gradient into the blood, whilst CO2 in the capillaries diffuses down the concentration gradient into the alveoli.

Question 2

Explain how alveoli are adapted for gas exchange.

Answer 2

• A large surface area to increase the rate of diffusion.
• A moist lining to dissolve gases.
• Thin walls to allow a short diffusion pathway.
• A good blood supply from the capillaries to maintain the concentration gradient.