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AS Level Biology - 9) Gas Exchange


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Like Membrane, this is one of the shorter topics with less content to go through. More or less an extension of the mamal transport system, the gas exchange system should still be seen as an individual self-serving/ self-functioning system worthy of its own spotlight.

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AS Level Biology - 9) Gas Exchange

  1. 1. Gas Exchange The Respiratory System and Smoking
  2. 2. The lung
  3. 3. The Lung  A thoracic chest cavity  Surrounded by pleural membranes  Enclose an airtight space  Small quantity of fluid for friction free movement and prevention of desiccation  Ventilation of the lung conducted by the movement of diaphragm/ ribs
  4. 4. Trachea  A tube leading from the throat to the lung  Has cartilage to keep in open, allow friction free movement and prevent the trachea from collapsing – arranged in C-shape rings  Has goblet cells which produces mucus  Has smooth muscle on the endothelium  Has cilia to sweep up the mucus  Is not the site of gas exchange
  5. 5. Bronchus  There are two bronchi at the base of the trachea  Has cartilage in irregular blocks  Has goblet cells  Has smooth muscle cells  Has cilia, and still not the site of gas exchange
  6. 6. Bronchioles  Branches off from bronchus  Surrounded by smooth muscles  Can contract or relax to control amount of air going in  E.g.. Relaxes during exercise for more flow of air  No cartilage – flexibility
  7. 7. Alveoli  Air sacs in the lung  Site of gas exchange  The walls – contain elastic fiber – stretch and recoil respectively when breathing in and out  Has thin wall – 0.5 micrometer  Pressed close against blood capillaries
  8. 8. Alveoli  A concentration gradient is always maintained where carbon dioxide would move in through the lung where there is lower concentration of CO2  Oxygen would move into capillaries where there is lower concentration of oxygen  Constant inhalation/ exhalation s well as blood flow keep this concentration gradient going
  9. 9. Warming/ Cleaning Air  Air flowing in is warmed to body temperature – to prevent desiccation  Particles of 5 – 10 micrometer will be caught by nasal hair  Mucus (made of mucin droplets which are glycoproteins) produced by goblet cells will capture dust, pollen grains, fungal spores, pathogens  Mucus produced by goblet cells – which has an enlarged upper part contain a mucin droplet and the rest of the cell slender like a stem
  10. 10. Warming/ Cleaning Air  Mucous gland also produces mucus from under the epithelium cell  Sulfur dioxide/ nitrogen dioxide can combine with mucus to form acidic solution – this may irritate the lining  Between goblets – ciliated cells 0 continuously beating the mucus up at 1cm/min  The mucus reaches the top of the trachea – it is swallowed down the esophagus – the pathogens destroyed by stomach acid  Macrophages also patrol the airway
  11. 11. Smoking  Smokes contain Tar/ Nicotine/ Carbon monoxide  CO and Nicotine damage the cardiovascular system  Tar/ Carcinogens damage the gas exchange system
  12. 12. Tobacco Smoking  Tar: mixture of compounds – settle in the airways – can lead to obstructive diseases  Tar contains carcinogens – can lead to lung cancer  Passive smoking is caused from side stream smoke (the burning tip) which is 85% of the smoke compared o the rest which is mainstream (mouth piece)
  13. 13. Lung Diseases  Air flows in the depth of the lung is slow  Allowing some particles to settle  May be airborne infections  COPD (Chronic Obstructive Pulmonary Diseases) are non infectious and can be caused by pollution and tobacco smoke
  14. 14. Chronic Bronchitis  Tar in cigarettes – cause mucus glands/ goblets to mutate and enlarge  Cilia are destroyed by tar  More production of mucus  Mucus accumulates in bronchioles  Smokers will attempt to cough them out
  15. 15. Chronic Bronchitis  The epithelium soon are replaced by scar tissue which due to its large size narrow the airway  Causes difficulty in breathing  Mucus allow for accumulation of bacteria such as one that causes pneumonia  This may lead to inflammation and more narrowing  Phlegm may be produced
  16. 16. Emphysema  Inflammation stimulates phagocytes to line the airway  To reach the airway, the phagocyte uses elastin (enzyme) to destroy alveoli and to make pathway  Alveoli can not expand  The bronchioles collapse and alveoli burst  This leads to less surface area and less capillary and less oxygen absorbed
  17. 17. Emphysema  Loss of elastin – difficult to move air out – make it hard to refresh air in the lung – the air becomes stagnant  Blood is not oxygenated  Blood vessels in the lung become more resistant 0 stimulating enlargement of right side of the heart
  18. 18. Lung Cancer  Tar can react with DNA in epithelial cells – or through breakdown products  Causes development of tumor  Cancer spreads through bronchial epithelium – into the lymphatic and to the rest of the body  Take 20 – 30 years to develop  Tissue damage can lead to coughing blood  Difficulty in breathing / chest pain
  19. 19. Lung Cancer  Bronchoscopy, Chemotherapy, CT scan can detect lung cancers  Lung cancers are usually discovered when they are advanced
  20. 20. Effects on the Cardiovascular system Nicotine:  absorbed very readily by the blood  Stimulates nervous system to reduce diameter of blood vessels  Release more adrenaline  Blood pressure increases – less blood flow to extremities  Increases risks of blood clotting