6.8 exchange of gases in the lungs

Question 1

rate of diffusion adaptations for alveoli

Answer 1

• red blood cells are slowed as they as through pulmonary capillaries-> more time for diffusion
• red blood cells are flat against the capillary wall-> short diffusion pathway
• alveoli and capillaries are thin-> short diffusion pathway
• alveoli and pulmonary capillaries-> large total surface area
• breathing-> constant concentration gradient
• blood flow-> maintains concentration gradient

Question 2

what is breathing a form of?

Answer 2

mass transport

Question 3

why is the diffusion pathway of the alveoli short?

Answer 3

single layer of epithelial cells

Question 4

why is the diffusion pathway of the blood capillaries short?

Answer 4

single layer of endothelial cells

Question 5

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.
[5 marks]

Answer 5

• Many alveoli provide a large surface area;
• Many capillaries provide a large surface area;
• fast diffusion;
• Alveoli or capillary walls thin
• short distance between alveoli and blood;
• squamous epithelium;
• So short diffusion pathway;
• So fast diffusion;
• Ventilation
• Maintains a diffusion gradient;
• So fast diffusion;