T2L1 The lungs and gas exchange

Question 1

Explain how the lungs are adapted for gas exchange

Answer 1

• Large surface area [to volume ratio] means that more gas can be diffused at any given moment

Good blood supply means that there is a high concentration gradient so a greater rate of diffusion

The lungs are moist which makes them good for dissolving gases for diffusion and prevent the adhesion of the alveoli

The alveoli and the walls of the capillary are very thin which decreased diffusion distance which increases the rate of diffusion

Question 2

Explain what Fick’s law is and show the equation

Answer 2

Fick’s law shows how the rate of diffusion is affected by surface area, concentration gradient and the thickness of the exchange surface

Rate of diffusion = surface area X conc gradient // diffusion distance

Question 3

Name an ddescribe the two types of cells in the airways

Answer 3

Goblet cells - secrete mucus

Squamous epithelial cells - flat increasing surface area

Question 4

Explain how sticky mucus in the lungs increases the chances of lung infection and decreases the rate of gas exchange

Answer 4

Bacteria and other pathogens can get trapped in the mucus that cause infection. When WBCs come to try and get rid of the pathogens and they break down they make the mucus even more sticky. The mucus is too thick for the cilia to waft up and sometimes this all leads to anaerobic conditions that some pathogens will thrive in.

Thick mucus can prevent gases diffusing into the alveoli which means that the rate of diffusion is decreased - the body receives less oxygen