Chapter 5 · Question 13
How are the lungs designed in human beings to maximise the area for exchange of gases?
Q13
How are the lungs designed in human beings to maximise the area for exchange of gases?
Answer Revealed
Direct Answer:
The lungs contain millions of tiny air sacs called alveoli, which provide a massive surface area with thin walls and a rich capillary network for efficient gas exchange.
Simple Explanation
Inside our lungs are millions of tiny balloon-like air sacs called alveoli. Their walls are extremely thin and surrounded by blood capillaries, so oxygen and CO2 can pass through very quickly.
Exam-Ready Structure
The human lungs are designed to maximise gas exchange through several structural adaptations: 1. Alveoli — The lungs contain millions of tiny, balloon-like structures called alveoli at the ends of bronchioles. This vast number creates an enormous total surface area (about 80-100 m2) for gas exchange. 2. Thin walls — The alveolar walls and capillary walls are each only one cell thick, minimising the diffusion distance. 3. Rich blood supply — Each alveolus is surrounded by a dense network of blood capillaries, ensuring continuous blood flow for efficient O2 uptake and CO2 removal. 4. Moist surface — The moist inner lining of alveoli helps gases dissolve before diffusion. 5. Elasticity — The elastic nature of alveoli allows them to expand during inhalation and recoil during exhalation.
Key Points
- Millions of alveoli provide huge surface area
- Alveolar and capillary walls are one cell thick
- Rich capillary network ensures efficient exchange
- Moist surface helps gases dissolve
Common Mistakes
- Saying gas exchange happens in bronchi or bronchioles instead of alveoli
- Forgetting to mention the thin walls
Relevant Maps and Figures
Human Respiratory System and Alveoli
diagram
Use the alveoli visual to justify the large surface area and thin-wall design of the lungs.
It is the best anchor for the structure-function part of the answer.
Use the alveoli diagram to connect large surface area, thin walls, and dense blood supply with efficient gas exchange in the lungs.
Answer Sources
- Figure 5.9 alveoli and respiratory systemfigure | Science | Life Processes | Human respiratory system | Pages 12