Lungs

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  • Created by: A
  • Created on: 05-04-13 13:58
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  • Lungs
    • structure
      • trachea - A flexible airway supported by rings of cartilage. The walls are made out of muscle lined with cilia and goblet cells
      • Bronchi- 2 divisions of the trachea. Also produce cilia (move dirt-laden mucus towardsthroat)
      • Bronchioles- series of branching subdivisions of the bronchi. Walls=muscle lined with epithelial cells allowing control over the flow of air in and out of the alveoli.
      • Alveoli-Minute air sacs at the end of the bronchioles. They contain collagen and elastic fibres (allow it to stretch), and lined with epithelium. The alveolar membrane is the gas exchange surface.
    • The rate of gas exchange is large because
      • high body temperature=high metabolic rate and high respiratory rates
      • Large organisms with a lot of living cells
    • mechanisms of breathing
      • pressure
        • When the air pressure of the atmosphere is greater than the air pressure inside the lungs, air is forced into the alveoli. visa versa
      • intercostal muscles
        • internal- contraction leads to expiration
        • external-contraction leads to inspiration
      • inspiration/  expiration
        • expiration: Internal intercostal muscles contract, ribs move down and in, decreasing the volume of the thorax. Diaphram relaxes into an arch. The decreaded volume increases pressure in the lungs air is forced out.
        • Inspiration: external intercostal muscles contract, ribs pulled up and out increasing the volume of thorax. The diaphram contracts and flattens. Increased volume= reduction of pressure in the lungs. air is forced into the lungs.
  • external-contraction leads to inspiration

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