How Lung Disease Affects Function

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  • How Lung Disease Affects Function
    • Pulmonary Tuberculosis is a Lung Disease Caused by Bacteria
      • Pulmonary tuberculosis is caused by the bacterium Mycobacterium tuberculosis
      • When someone becomes infected with tuberculosis bacteria, immune system cells build a wall around the bacteria in the lungs. This forms small, hard lumps known as tubercles
        • Infected tissue within the tubercles dies, the gaseous exchange surface is damaged so tidal volume is decreased
          • Tuberculosis also causes fibrosis which further reduces the tidal volume
            • If the bacteria enter the bloodstream, they can spread to other parts of the body
      • Common symptoms include persistent cough, coughing up blood and mucus, chest pains, shortness of breath and fatigue
        • Sufferers may also have a fever
          • Many lose weight due to loss in appetite
      • TB is transmitted by droplet infection - when an infected person coughs or sneezes, tiny droplets of saliva and mucus containing the bacteria are released from their mouth and nose. If an uninfected person breathes in these droplets, the bacteria are passed on
        • Tuberculosis tends to be much more widespread in areas where hygiene levels are poor and where people live in crowded conditions
          • TB can be prevented with the BCG vaccine and can be treated with antibiotics
      • Many people with TB are asymptomatic - theyre infected by they dont show any symptoms because the infection is in an inactive form. People who are asymptomatic are unable to pass the infection on. But if they become weakened e.g. by another diseases then the infection can become active. Theyll show the symptoms and be able to pass on the infection
    • Emphysema
      • Emphysema is a lung disease caused by smoking or long term exposure to air pollution - foreign particles in the smoke become trapped in the alveoli
        • This causes inflammation, which encourages phagocytes to the area. The phagocytes produce an enzyme that breaks down elastin
          • The alveolar walls are destroyed and the elasticity of the lungs is lost
            • This reduces the surface area of the alveoli, so the rate of gaseous exchange decreases
              • Symptoms of emphysema include shortness of breath and wheezing. People with emphysema have an increased breathing rate as they try to increase the amount of air reaching their lungs
    • Fibrosis and asthma affect lung function
      • Fibrosis and asthma reduce the rate of gas exchange in the alveoli. Less oxygen is able to diffuse into the bloodstream, the body cells receive less oxygen and the rate of aerobic respiration is reduced. This means less energy is released and sufferers often feel tired and weak.
        • Fibrosis
          • Fibrosis is the formation of scar tissue in the lungs. This can be the result of an infection or exposure to substances like asbestos or dust.
            • Scar tissue is thicker and less elastic than normal lung tissue
              • This means that the lungs are less able to expand and so cant hold as much air as normal - the tidal volume is reduced. Its also harder to force air out of the lungs due to the loss of elasticity
                • Theres a reduction in the rate of gaseous exchange - diffusion is slower across a thick scarred membrane
                  • symptoms include shortness of breath, a dry cough, chest pains, fatigue and weakness
                    • Fibrosis sufferers have a faster breathing rate than normal - to get enough air into their lungs to oxygenate their blood
        • Asthma
          • Asthma is a respiratory condition where the airways become inflamed and irritated. The causes vary from case to case but its usually because of an allergic reaction to substances such as pollen and dust
            • During an asthma attack, the smooth muscle lining the bronchioles contracts and large amount of mucus is produced
              • This causes constriction of the airways, making it difficult for the sufferer to breathe properly. Air flow in and out of the lungs is severely reduced, so less oxygen enters the alveoli and moves into the blood
                • Symptoms include wheezing, a tight chest and shortness of breath. During an attack the symptoms come on very suddenly. They can be relieved by drugs which cause the muscles in the bronchioles to relax opening the airways


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