Perfect Adaptations for Gas Exchange
Alveoli are perfectly adapted for efficient gas exchange through several key features:
1. Enormous Surface Area
- ~300 million alveoli provide ~70mยฒ total surface area
- Greatly increases rate of diffusion
- Like having the area of a tennis court in your chest
2. Extremely Thin Walls
- Alveolar walls just one cell thick (0.5 micrometers)
- Capillary walls also one cell thick
- Total diffusion distance โค 1 micrometer
- Allows rapid gas exchange by diffusion
3. Rich Blood Supply
- Dense network of capillaries around each alveolus
- Blood flow maintains concentration gradients
- Continuous removal of Oโ and delivery of COโ
4. Moist Surface
- Thin layer of moisture dissolves gases
- Essential for diffusion across membranes
- Contains surfactant to prevent collapse
This deep dive covers Alveoli: The Sites of Gas Exchange within Gas Exchange in Humans for GCSE Biology. Lung structure, alveoli adaptations, breathing mechanism, gas transport in blood, and effects of smoking It is section 3 of 19 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Gas Exchange in Humans
Which is the correct order of structures air passes through to reach the lungs?
Explain how the structure of alveoli is adapted for efficient gas exchange.
Quick recall flashcards
What are alveoli?
Tiny air sacs in the lungs where gas exchange takes place - oxygen enters the blood and carbon dioxide leaves
What is the trachea?
The main airway (windpipe) that carries air from the throat to the lungs, reinforced with cartilage rings