Lung Function and lung disease

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  • Created by: Rachel98
  • Created on: 18-05-15 15:23
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  • Lung Function and Disease
    • Lungs are specialised for gas exchange
      • 1) Air enters the trachea when we breath in
      • 2) The trachea splits into two bronchi. One bronchus leads to each lung
      • 3) Each bronchus then branches off into bronchioles which are smaller tubes
      • 4) The bronchioles end in alveoli which are small air sacs where gas exchange occurs.
    • Ventilation is breathing in and out
      • Inspiration
        • 1) The diaphragm and the intercostal muscles contract
        • 2) Causing the ribcage to move upwards and out while the diaphragm flattens. Increasing the volume of the thorax
        • 3) As the thorax cavity volume increases, the lung pressure decreases to below atmospheric pressure
        • 4) This cause air to flow into the lungs
        • This is a active process: It requires energy
      • Expiration
        • 1) The diaphragm and intercostal muscles relax
        • 2) The ribcage moves downwards and inwards while the diaphragm becomes curved again
        • 3) The thorax volume decreases, causing air pressure in the lungs to increase above atmospheric pressure.
        • 4) This causes air to be forced out of the lungs
        • This is a passive process: It doesn't require energy
    • Alveoli are adapted for gas exchange
      • A thin exchange surface - the alveolar epithelium is only one cell thick.
        • Reducing diffusion distance
          • Increasing rate of diffusion
            • Large surface area - There are many alveoli which increase surface area for gas exchange to occur
      • Large surface area - There are many alveoli which increase surface area for gas exchange to occur
      • Good transport system- there are many capillaries surrounding all of the alveoli
        • Maintaining the concentration gradient of oxygen and carbon dioxide
          • Increasing rate of diffusion
      • Pulmonary Tuberculosis
        • Infection
          • 1) When a person is infected with the tuberculosis bacteria, the immune system cells build a wall around the bacteria in the lungs.
            • Forming small, hard lumps called tubercules
            • 2) Infected tissue within the tubercles dies.
              • The gas exchange surface is damaged so tidal volume is decreased
              • 3) Tuberculosis also causes fibrosis, further decreasing tidal volume
                • 4) If the bacteria enter the bloodstream, they can spread to other parts of the body.
        • Symptoms
          • Persistent cough
          • coughing up blood and mucus
          • chest pains
          • shortness of breath
          • fatigue
          • fever
          • Many lose weight due to a loss of appetite
        • Transmission
          • Transmitted by droplet infection
            • If an infected person sneezes or coughs, droplets of saliva and mucus containing bacteria are released
              • If an uninfected person breaths in these droplets, the bacteria is passed on to them
          • TB tends to be more widespread in areas where hygiene levels are poor and where conditions are crowded
          • TB can be prevented with the BCG vaccine and can be treated with antibiotics
      • Fibrosis
        • This is the formation of scar tissue in the lungs.
          • It results from an infection or exposure to irritants such as dust and asbestos
          • Scar tissue is thicker and less elastic than normal lung tissue
            • SO the lungs are less able to expand meaning that they can't hold as much air as normal. the tidal volume is reduced
              • It is also harder to force air out of the lungs.
                • Rate of gas exchange is reduced due to a thicker exchange surface and a lower concentration gradient
                  • Both of these are factors which will reduce the rate of diffusion according to Fick's Law.
        • Symptoms
          • shortness of breath
          • dry cough
          • chest pains
          • fatigue/ weakness
          • sufferers have a faster breathing rate than normal.
            • This is to allow the to get enough oxygen to oxygenate their blood
      • Asthma
        • a respiratory condition were the airways become inflamed and irritated.
          • usually caused by an allergic reaction to dust or pollen
            • During an attack the smooth muscle lining the bronchioles contract
              • And a large amount of mucus is produced.
              • This cause constriction of the airways making it difficult to breath
                • Air flow into the lungs is severely reduced so less oxygen enters the blood
                  • Symptoms
                    • weezing
                    • tight chest
                    • shortness of breath
                  • Treatment
                    • Symptoms come on very suddenly during attacks and can be relived by drugs
                    • Usually an inhaler.
                      • Relaxes the muscles in the bronchioles to open up the airways
                        • Symptoms come on very suddenly during attacks and can be relived by drugs
      • Emphysema
        • A lung disease caused by long term exposure to irritants such as air pollen or smoking.
          • Foreign particles in the air become trapped in the alveoli.
            • This causes inflammation which attracts phagocytes to the area.
              • The phagocytes then release an enzyme that digests the elastin in the walls of the alveoli
                • This results in the loss of elasticity in the lungs.
                  • This means that the alveoli can't recoil and expel as well.
                    • It also leads to the break down of walls. Increasing the diffusion distance and decreasing surface area.
                      • Increasing rate of diffusion and reducing the efficiency of gas exchange.
                • Symptoms
                  • shortness of breath
                  • wheezing
                  • increased breathing rate in order to gain enough oxygen into the lungs to oxygenate the blood.

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