Dissecting gas exchange systems

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  • Dissecting Gas Exchange Systems
    • Lungs
      • 1) Need lab coat, clean and sharp dissecting tools- blunt tools dangerous
      • 2) Lay lungs on cutting board. Should be able to see trachea and two bronchi
      • 3) To see lungs inflate, attach rubber tubing to trachea and pump air. Lungs deflate because of elastin in walls of alveoli
      • 4) Trachea supported by c shaped cartilage rings
      • 5) Open trachea length ways, cut down opening of rings. Scalpel: cut downwards, don't apply too much pressure
      • 6) Continue cutting down bronchi. Should see bronchioles branching off
      • 7) Cut off piece of lung. Tissue feels spongy because of air trapped in alveoli
      • 8) Wash hands and disinfect work surfaces
    • Fish Gills
      • 1) Wear apron/lab coat
      • 2) Place fish on dissecting tray/cutting board
      • 3) Gills protected by bony flap called operculum and gill arches
      • 4) To remove gills push back operculum and use scissors to remove gills. Cut each gill arch through bone at top and bottom
      • 5) Should be able to see gill filaments
    • Insects
      • 1) Fix insect to dissecting board- use dissecting pins through legs to hold in place
      • 2) To examine tracheae, cut and remove piece of exoskeleton from length of abdomen
      • 3) Use syringe to fill abdomen with saline solution- should see network of very thin, silvery grey tubes, tracheae filled with air
      • 4) Examine under optical using temporary mount slide. Should be able to see rings of chitin in walls of tracheae- for support
    • Ethical Issues
      • 1) Morally wrong to kill just for dissections, unnecessary killing
      • 2) Animals used not always raised in humane way- subject to overcrowding, extremes of temperature, lack of food, may not be killed humanely

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