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Gaseous Exchange System

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  • 7/28/2019 Gaseous Exchange System


    Human Respiratory System

  • 7/28/2019 Gaseous Exchange System


    Gaseous Exchange

    This process involves the passage of gases

    such as oxygen into, and carbon dioxide out of

    cells or a transport system.

    First, air needs to be in contact with the

    gaseous exchange surface

    This is achieved by breathing

    See picture over the page of the respiratory


  • 7/28/2019 Gaseous Exchange System


  • 7/28/2019 Gaseous Exchange System


  • 7/28/2019 Gaseous Exchange System


    Examiners Tip

    To remember the sequence of structures

    through which air passes when you breathe in

    imagine an apple tree:

    Trunk Trachea

    Bough Bronchus

    Branch BronchioleApples Alveoli

  • 7/28/2019 Gaseous Exchange System


  • 7/28/2019 Gaseous Exchange System



    Small invertebrates, such as earthworms, takein oxygen over their skin surface

    They need to have a large surface area to

    obtain sufficient oxygen, and their skin is thinand moist

    Examples of gaseous exchange surfaces are the

    alveoli in the lungs of mammals and gills of fish see over page for the structure of thealveolus

  • 7/28/2019 Gaseous Exchange System


  • 7/28/2019 Gaseous Exchange System


    Inspired Air


    Expired Air



    en 79 79 Not used or produced by body


    n 21 16 Used up in the process of


    n Dioxide 0.04 4 Produced in the process of


    Vapour Variable Saturated Produced in the process ofrespiration, moisture evaporate

    from the surface of the alveoli

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    Testing for Carbon Dioxide

    Two chemical reagents can used to test for carbondioxide - they change colour when the gas isbubbled through.

    You only need to remember one

    1. Limewater changes from colourless to milky

    2.Hydrogencarbonate changes from red to yellow

    Expired air makes these reagents change colourmore quickly than inspired air because there ismore carbon dioxide present in expired air

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    Effects of Physical Activity on

    Breathing The volume of air breathed in and out during normal, relaxed

    breathing is about 0.5litres

    This is the tidal volume

    The breathing rate is about 12 breaths per minute

    During exercise, the volume inhaled (depth) increases to about 5litres (depending on the age, sex, size and fitness of the person)

    The maximum amount of air breathed in or out in one breath is thevital capacity

    The breathing rate can increase to over 20 breaths per minute

    The total lung volume is greater than the vital capacity becausesome air always remains in the lungs (otherwise the lungs wouldcollapse and the alveoli walls would stick together)

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  • 7/28/2019 Gaseous Exchange System



    1a) (i) Inspired air contains more oxygen, less carbondioxide and less water vapour than expired air

    (ii) Three features: 1. the wall of the alveolus is one

    cell thick (or very thin) 2. there is a moist surface tothe alveoli 3. there are large numbers of alveoli 4.the air in the alveoli is constantly being replaced

    b) (i)The release of energy by cells without the use ofoxygen

    (ii) In muscle cells

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