Chapter 4 - Structure of the Human Gas-Exchange System

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  • Created on: 25-03-14 14:57
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  • Functions and Structure of the Human Gas-Exchange System
    • Lungs
      • A pair of lobed structures
      • Made up of a series of highly branched tubules, called bronchioles which end in tiny air sacs called alveoli
    • Trachea
      • Is a flexible airway that is supported by rings of cartilage
      • The cartilage prevents the trachea collapsing as the air pressure inside falls when breathing in.
      • The tracheal walls are made up of muscle, lined with ciliated epithelium and goblet cells.
      • The goblet cells produce mucus that traps dirt particles bacteria from the air breathed in.
      • The cilia move the mucus, laden with dirt and microorganisms, up to the throat, from where it passes down the oesophagus into the stomach
    • Bronchi
      • Are two divisions of the trachea, each lending to one lung
      • They are similar in structure to the trachea and, like the trachea, they also produce mucus to trap dirt particles and have cilia that move the dirt-laden mucus towards the throat
      • The larger bonchi are supported by cartilage, although the amount of cartilage is reduced as the bronchi get smaller
    • Bronchioles
      • Are a series of branching subdivisions of the bronchi
      • Their walls are made of muscle lined with epithelial cells. This muscle allows them to constrict so that thye can control the flow of air in and out of the alveoli
    • Alveoli
      • Are minute air-sacs at the end of the bronchioles
      • They contains some collagen and elastic fibres, and they ar elined with epithelium.
      • The elastic fibres allow the alveoli to stretch as they fill with air when breathing in. They then spring back during breathing out in order to expel the CO2-rich air. The alveoli membrane is the gas exchange surface


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