1.6.8

The Respiratory System

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Exchange Surfaces

Exchange surfaces are surfaces that are adapted to maximise the efficiency of gas and solute (a substance dissolved in a liquid) exchange across them. Exchange surface such as alveoli have the following adaptations:

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Large surface area

  • A large surface area allows more of a substance to diffuse at the same time.
  • Alveoli create a large surface area for gas exchange in the lungs.
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Thin membrane

  • A thin membrane reduces the diffusion distance.
  • Alveoli are one cell thick.
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Blood supply

  • Where substances are exchanged through blood in animals, exchange surfaces are densely packed with blood vessels:
    • These blood vessels replenish the blood supply to maintain a high concentration gradient by bringing in new blood as diffusion starts to even out the concentrations.
  • There are many capillaries around the alveoli.
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Ventilation

  • In animals, if a gas is exchanged, the surface is ventilated (through breathing) to maintain a high concentration gradient and increase the rate of exchange.
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Kept clear

  • Any particles of dust for example will block an exchange surface and reduce the rate of exchange.
  • Goblet cells and cilia cells line the airways to prevent this.
  • Goblet cells produce sticky mucus that traps particles and cilia cells waft the mucus up and out of the airway.

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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