Gaseous Exchange

  • Created by: alanahart
  • Created on: 14-05-15 19:28
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  • Features of a good exchange system
    • Thin barrier/wall
      • Alveoli and capillary walls are one squamous cell thick
    • Large surface area
      • Numerous amounts of tiny alveoli
    • Gaseous Exchange
      • Tissues
        • Tissues in the Lungs
          • Trachea & Bronchi
            • Majority consists of cartilage.   C-rings in trachea and less regular in bronchi
            • Inside cartilage is layer of glandular tissue, connective tissue, elastic fibres. smooth muscle and blood vessels.
            • Inner lining, is an epithelium layer consisting of 2 types of cell. Ciliated epithelium and goblet cells.
          • Bronchioles
            • Narrower, so less or no cartiage
            • Mostly smooth muscle and elastic fibres
            • Smallest bronchioles have alveoli at the ends.
        • Cartilage has a structural role. It supports the trachea and bronchi, holding them open. If they didnt, the airway would collapse from the low air pressure during inhalation.
        • Smooth muscle contracts, which constricts the airway making a narrow lumen. This affect mostly takes place in bronchioles and will restrict airflow. This is often done if there is a harmful substance. It is involuntary and is a cause of asthma.
        • Elastic fibres help with the reformation of the airway after S.M. has contracted. Once it relaxes, the E.F. recoil, dilating the airway.
        • Goblet cells and glandular tissue secrete mucus to trap tiny particles such as pollen and bacteria.
        • Ciliated epithelium are ciliated cells. Cilia are hair-like projections that waft mucus up airway to back of the throat. Here, they are swallowed and acidity in stomach kills any bacteria.
      • Measuring Lung Capacity
        • Tidal volume: volume of air moved in and out of lungs with eavh breath while at rest. Approx. 0.5 dm3.
          • Needs to provide body with enough O2 whilst moving enough CO2 to maintain a safe level
        • Vital capacity: Lagest volume of air that can be moved in and out of lungs in any one breath. Approx. 5 dm3 but varies with gender, size and age. Regular activity increases V.C.
        • Residual volume: volume of air that always remains in lungs even after possible exhalation. Approx. 1.5 dm3
        • Dead space: air in bronchioles, bronchi and alveoli. There is no gaseous exchange.
        • Inspiratory reserve volume: how much more air can be breathed in above normal T.V. Used when exercising
        • Expiratory reserve volume: how much more air can be breathed out above normal T.V.
        • Spirometer: chamber filled with O2 that floats on tank of water. Breathing in takes O2 from chamber so it sinks down and breathing out pushes air into chamber so floats up
          • Level of CO2 can increase dangerously in spirometer, so soda lime is used to absorb CO2 that is exhaled. This means that the total volume of gas in the chamber decreases.
            • Vol of O2 inhaled= Vol of CO2 exhaled. As CO2 is removed, the total reduction is equal to amount of O2 used up so we can measure O2 usage under different conditions
    • Fresh supply of molecules one side
      • Blood brings CO2 to lungs so the concentration of CO2 in blood is higher than in alveoli
    • Removal of required molecules the other side
      • To maintain  a steep diffusion gradient
        • Fresh supply of molecules one side
          • Blood brings CO2 to lungs so the concentration of CO2 in blood is higher than in alveoli
      • Blood also takes away the O2 from the lungs ensuring the conc. in blood is lower than conc. of air in alveoli.


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