Human Physiology and Pathology-Respiration

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  • Created by: jessica
  • Created on: 06-02-13 14:20
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  • Respiration
    • Lung structure and function
      • Large surface area for gas exchange
      • Have a role in acid base balnce
        • Water and CO2 combine to form carbonic acid
      • Involved in speech and breath control
      • Respiratory system
        • Nasal passage, oral cavity, pharynx, larynx, trachea and lungs
        • Trachea goes into bronchi, goes into bronchioles to alveoli
          • Alveolar sacs make up 50-100m2 surface area.
            • Alveoli contain type 1 and type 2 epithelial cells
        • Made of conducting and respiratory zone
          • Respiratory zone
            • terminal bronchioles to alveoli
              • Alveolar ventilation
                • Va=(Vt x RR)- (DSV-RR)
                • the measure of fresh air volume reaching the alveoli per minute
          • Conducting zone
            • Larynx to terminal bronicholes
            • considered dead space as it doesnt involve gas exchange
      • Diaphragm contracts for inspiration
      • Nasal turbinates circulate, humidify air
      • Mucociliary escalator
        • cilia beat mucus up and out of the lungs/respiratory tract taking dust and bacteria with it
    • Lung ventilation
      • Pressures
        • Partial pressure of oxygen during inspiration is 149mmHg
        • Gases have different partial pressures
        • Pressure of the air at sea level is 760mmHg
        • SVP=Saturated vapour pressure (when water is present in the gases)
        • Intrapleural pressure
          • -5cmH2O at end expiration when there is no gas flow
        • Transpulmonary pressure
          • The force acting on the lungs to expand
        • Larger in small alveoli when the adjacent one has the same surface tension
          • Pulmonary surfactant released in small avleoli to prevent the collapse of the alveoli
      • Flow=Pressure difference/R
        • Pressure difference= atmospheric pressure-alveolar pressure
      • Muscles of respiration
        • Sternocleidomastoid, Scalene muscles, external intercostal muscles and diaphragm used for inspiration
        • Internal intercostal muscles, external oblique, internal oblique and rectus abdomens used for active respiration
      • Lung compliance
        • stretchiness of the lungs
        • Compliance= change in lung volume/ transpulmonary pressure
        • Large lung compliance better
    • Gas transport in the blood and control of respiration
      • Henry's Law-gas in solution is proportional to partial pressure of gas and solubility of gases.
      • Lungs have two circulations-pulmonary and bronchiole
      • Fick's Law
        • Vgas=A.P.(P1-P2)/T
      • Erythrocytes
        • Hb molecule has 4 subunits. Haem groups contains Fe for  binding to O2.
      • Respiration controlled by pons, medulla,
        • Peripheral and central chemoreceptors detect changes in PO2 and PCO2, interacting with the brain to inspire/expire
    • Respiratory diseases
      • Respiratory failure when PO2 is less than 60mmHg at sea level
      • Obstructive diseases
        • increased resistance to airflow
      • Lung function tests
      • Restrictive diseases
        • Expansion of lungs restricted


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