Unit 1 Section 3.1.4 The Lungs

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  • The Lungs
    • Structure
      • Trachea
        • Flexible airway - rings of cartilage for support
      • Bronchi
        • Contain mucus - traps dust. Cilli, movement
      • Bronchioles
        • Smaller, made of muscle. Constrict - control air flow
      • Alveoli
        • Tiny air sacs. Allow diffusion of O2 into blood and C02 from blood to air
    • Breathing Mechanism
      • Inhalation
        • EIM contract, IIM relax
          • Rib cage - up and out
            • Diaphragm - flattens
              • Vol. increases, pressure decreases
                • Air forced into lungs
      • Exhalation
        • IIM contract, EIM relax
          • Rib cage - down and in
            • Diaphragm relaxes - domed position
              • Vol. decreases, pressure increases
                • Air forced out of lungs- into atmosphere
    • Exchange Surfaces
      • Large s.a to vol. ratio
        • Speeds up exchange rate
      • Very thin
        • Short diffusion pathway
      • Partially permeable
        • Selective about transport
      • Movement, circulation
        • Maintain steep conc. gradient
    • Diseases
      • Pulmonary Fibrosis
        • Scars forming on epithelial of lungs
          • Thickens them. Irreversible
            • Diffusion of O2, less efficient
              • Lung capacity reduced
                • Reduced elastin
                  • Breath loss, cough, chest pain, fatigue
      • Asthma
        • Localised allergic reaction
          • Cause - release histamine
            • Airway linings inflamed
              • More mucus from epithelials
                • Fluid leaves cappilaries
                  • Entering airways
                    • Surrounding muscle contract
                      • Restrict airflow
                        • Difficult breathing, wheezy, tight chest, cough
      • Emphysema
        • Lungs elastic = permanently stretched
          • Air can't be forced out of alveoli
            • S.a of alveoli reduced
              • Can burst
                • Little gas exchange can occur
                  • Breath loss, cough, bluish skin colouration

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