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01 The Respiratory System

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01 The Respiratory System

  1. 1. GAS EXCHANGE ALBIO9700/2006JK
  2. 2. The gaseous exchange system Cleans and warms air that enters during breathing Maximises the surface area for diffusion of O2 and CO2 between blood and atmosphere Minimises the distance for this diffusion Maintains adequate gradients for this diffusion ALBIO9700/2006JK
  3. 3. The Respiratory System Nasal cavity: air passing over the A flap of elastic mucous membrane of tissue that the nasal cavity is forms a lid moistened, warmed over the and filtered opening of the trachea Passage where the nose and mouth come togetherContains 2 ligaments (vocalcords) that produce soundwhen air move through them ALBIO9700/2006JK
  4. 4. Lungs Site of gaseous exchange between air and blood Presents a huge surface area to the air that flows in and out In the thoracic (chest) cavity surrounded by airtight space containing fluid to allow friction-free movement ALBIO9700/2006JK
  5. 5. Alveoli Have very thin epithelial lining Surrounded by many blood capillaries Alveolar walls contain elastic fibres which stretch during breathing and recoil during expiration to help force out air – allows alveoli to expand ALBIO9700/2006JK
  6. 6. Alveoli (cont) ALBIO9700/2006JK
  7. 7. Gas exchange in alveoli ALBIO9700/2006JK
  8. 8. BRAIN TEASERHow many times must a molecule of oxygendiffuse across a cell surface membrane inpassing from the inside of an alveolus tohaemoglobin?
  9. 9. How does the composition of inhaled air compare to that of exhaled air? % Gas Atmospheric air Alveolar air (inhaled air) (exhaled air) Nitrogen 79.0% 79.0% Oxygen 20.9% 14.0%Carbon dioxide 0.04% 5.6%Water vapour 1.0% 6.0% ALBIO9700/2006JK
  10. 10. ALBIO9700/2006JK
  11. 11. The ciliatedepithelium
  12. 12. TRACHEA
  13. 13. The Lung Tissues
  14. 14. Bronchiole and Trachea in transverse section
  15. 15. A transverse cross section view of the cartilaginous trachea cartilage Smooth muscle And elastic fibresCiliated epitheliumand goblet cells
  16. 16. Cartilage Ciliated Smooth Connective epithelium muscle tissue with goblet cells Trachea √ √ √ √Two bronchi √ √ √ √Bronchiole Cartillage No goblet Gradually √ gradually lost lost Alveolar No cartilage No cilia No No duct No gobletAlveolar sac No cartilage No cilia No No No goblet Alveoli No cartilage No cilia No No No goblet ALBIO9700/2006JK
  17. 17.  Cartilage: prevents collapse of the tube during inspiration. Cilia: beats rhythmically, gradually sweeping the mucus up towards the back of the throat, where it is swallowed. Goblet cells: secretes a protective coating called mucus. Much of the dust and microorganisms in the air which is breathed in is trapped in this mucus. Smooth muscle: involuntary muscles. When they contract, they narrow the airways. ALBIO9700/2006JK
  18. 18. Lung volumes and capasities Tidal volume: the volume of gas exchange during one breath in and out. ~450 cm3 during quiet breathing. After exercise it rises to ~3 dm3. Vital capacity: maximum volume of air that a person can exhale after filling the lungs to their maximum extent. ALBIO9700/2006JK
  19. 19. Task1. State 3 ways in which the structure of the lungs allows efficient gas exchange (4).2. Explain why the barrier to diffusion must be as thin as possible (1).3. Describe how a steep diffusion gradient is achieved in the lungs (4).
  20. 20. Answers1. State 3 ways in which the structure of the lungs allows efficient gas exchange (4). Large surface area (1) provides more space for molecules to pass through (1), plasma membranes surrounding the cytoplasm create a permeable barrier allowing diffusion of oxygen and carbon dioxide (1), alveolus wall is one cell thick creating a thin barrier for diffusion (1)2. Explain why the barrier to diffusion must be as thin as possible (1). It reduces the distance gases have to diffuse (1)
  21. 21. Answers1. Describe how a steep diffusion gradient is achieved in the lungs (4). Blood brings carbon dioxide from the tissues to the lungs ensuring the carbon dioxide concentration in the blood is higher than that of the air in the alveoli (1), it also carries oxygen away from the lungs ensuring that the concentration of oxygen in the blood is kept lower than air inside the alveoli (1), the movement of the lungs (ventilation) ensures there is a fresh supply of oxygen entering the lungs increasing the concentration of oxygen in the alveoli (1), carbon dioxide is also removed by ventilation ensuring that the concentration in the alveoli is lower than that of the blood (1)
  22. 22. Mechanism of ventilationExternal intercostal musclescontract and the internal External intercostal musclesintercostal muscle relax relax and the internal intercostal muscle contractPulls rib cage up and out The rib cage drops, mainlyDiaphragm muscles contract due to its own weightThis flattened the diaphragm Force the diaphragm into domed shapeBoth actions increase thevolume of the thorax Diaphragm muscles relaxPressure in the thorax, hence Pressure in the thorax,the lung, is reduced to less hence the lung, is increase,than atmospheric pressure more than atmospheric pressureAir enters the lungs, inflatingthe alveoli, until the air Air is forced out of the lungspressure in the lungs is equalto that of the atmosphere ALBIO9700/2006JK

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