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Biology_A-level_Cie

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  1. 1-1-the-microscope-in-cell-studies
    5 主题
  2. 1-2-cells-as-the-basic-units-of-living-organisms
    5 主题
  3. 2-1-testing-for-biological-molecules
    3 主题
  4. 2-2-carbohydrates-and-lipids
    8 主题
  5. 2-3-proteins
    6 主题
  6. 2-4-water
    2 主题
  7. 3-1-mode-of-action-of-enzymes
    5 主题
  8. 3-2-factors-that-affect-enzyme-action
    8 主题
  9. 4-1-fluid-mosaic-membranes
    4 主题
  10. 4-2-movement-into-and-out-of-cells
    12 主题
  11. 5-1-replication-and-division-of-nuclei-and-cells
    6 主题
  12. 5-2-chromosome-behaviour-in-mitosis
    2 主题
  13. 6-1-structure-of-nucleic-acids-and-replication-of-dna
    4 主题
  14. 6-2-protein-synthesis
    5 主题
  15. 7-1-structure-of-transport-tissues
    4 主题
  16. 7-2-transport-mechanisms
    7 主题
  17. 8-1-the-circulatory-system
    7 主题
  18. 8-2-transport-of-oxygen-and-carbon-dioxide
    5 主题
  19. 8-3-the-heart
    4 主题
  20. 9-1-the-gas-exchange-system
    6 主题
  21. 10-1-infectious-diseases
    3 主题
  22. 10-2-antibiotics
    3 主题
  23. 11-1-the-immune-system
    4 主题
  24. 11-2-antibodies-and-vaccination
    6 主题
  25. 12-1-energy
    5 主题
  26. 12-2-respiration
    11 主题
  27. 13-1-photosynthesis-as-an-energy-transfer-process
    8 主题
  28. 13-2-investigation-of-limiting-factors
    2 主题
  29. 14-1-homeostasis-in-mammals
    8 主题
  30. 14-2-homeostasis-in-plants
    3 主题
  31. 15-1-control-and-coordination-in-mammals
    12 主题
  32. 15-2-control-and-coordination-in-plants
    3 主题
  33. 16-1-passage-of-information-from-parents-to-offspring
    5 主题
  34. 16-2-the-roles-of-genes-in-determining-the-phenotype
    7 主题
  35. 16-3-gene-control
    3 主题
  36. 17-1-variation
    4 主题
  37. 17-2-natural-and-artificial-selection
    7 主题
  38. 17-3-evolution
    2 主题
  39. 18-1-classification
    5 主题
  40. 18-2-biodiversity
    7 主题
  41. 18-3-conservation
    6 主题
  42. 19-1-principles-of-genetic-technology
    11 主题
  43. 19-2-genetic-technology-applied-to-medicine
    4 主题
  44. 19-3-genetically-modified-organisms-in-agriculture
    2 主题
  45. 1-1-the-microscope-in-cell-studies
  46. 1-2-cells-as-the-basic-units-of-living-organisms
  47. 2-1-testing-for-biological-molecules
  48. 2-2-carbohydrates-and-lipids
  49. 2-3-proteins
  50. 2-4-water
  51. 3-1-mode-of-action-of-enzymes
  52. 3-2-factors-that-affect-enzyme-action
  53. 4-1-fluid-mosaic-membranes
  54. 4-2-movement-into-and-out-of-cells
  55. 5-1-replication-and-division-of-nuclei-and-cells
  56. 5-2-chromosome-behaviour-in-mitosis
  57. 6-1-structure-of-nucleic-acids-and-replication-of-dna
  58. 6-2-protein-synthesis
  59. 7-1-structure-of-transport-tissues
  60. 7-2-transport-mechanisms
  61. 8-1-the-circulatory-system
  62. 8-2-transport-of-oxygen-and-carbon-dioxide
  63. 8-3-the-heart
  64. 9-1-the-gas-exchange-system
  65. 10-1-infectious-diseases
  66. 10-2-antibiotics
  67. 11-1-the-immune-system
  68. 11-2-antibodies-and-vaccination
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Distribution of tissues in the gas exchange system

Cartilage

  • Cartilage is a strong and flexible tissue found in various places around the body

    • Cartilage forms ‘c’ shaped rings that are arranged along the trachea, called tracheal rings

      • These rings help to support the trachea and ensure it stays open, while allowing it to move and flex while we breathe

    • Cartilage also supports the bronchi, though it does not form c-shaped rings here

    • Cartilage is not found in the bronchioles

Ciliated epithelium

  • Ciliated epithelium is a specialised tissue which lines all of the tubes of the airways

    • Each cell has small projections of cilia

    • The cilia sweep mucus, dust and bacteria upwards and away from the lungs and the epithelium itself

Diagram of epithelial cells with labelled cilia, nucleus, goblet cell, and basement membrane, showing structural arrangement and cell components.
Ciliated epithelium showing cilia, basement membrane, goblet cell and nucleus

Goblet cells

  • Goblet cells can be found scattered throughout the ciliated epithelium in the trachea, and also in the bronchi, though usually not in the bronchioles

    • They are mucus-producing cells that secrete viscous mucus

    • This mucus traps dust, bacteria and other microorganisms and prevents them from reaching the lungs

    • The mucus is then swept along by the cilia of the ciliated epithelium upwards and is swallowed

    • The mucus and any microorganisms will then be destroyed by the acid in the stomach

Squamous epithelium of alveoli

  • The alveoli have a lining of thin squamous epithelium, that allows for gas exchange

    • The squamous epithelium forms the structure of the alveolar wall and is very thin and permeable for the easy diffusion of gases

Smooth muscle

  • Smooth muscle can be found in the walls of the trachea, bronchi and bronchioles

    • It helps to regulate the flow of air into the lungs by relaxing when more air is needed and constricting when less air is needed

Capillaries

  • Each alveolus is surrounded by an extensive network of capillaries

    • Carbon dioxide diffuses out of the capillaries and into the alveoli to be exhaled, while oxygen diffuses the other way from alveoli and into the capillaries to be carried around the body

    • These capillaries have a diameter of around 3-4 µm, which is only wide enough for one red blood cell to travel through at any one time

      • This ensures that there is sufficient time and opportunity for gas exchange to occur

Worked Example

Explain how the lining of the trachea, bronchus and bronchioles provide protection against pathogens

  • Cilia beat to move mucus away from the lungs and up towards the mouth

  • Mucus is produced by goblet cells and acts as a barrier to pathogens from entering the ciliated epithelium

  • The mucus also traps bacteria and microorganisms, while blood vessels bring macrophages to engulf any pathogens in phagocytosis