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Circulation and gas exchange II (Chapter 42)

Learn about the intricate structures like fish gill filaments, insect tracheal systems, and mammalian lungs that are crucial for gas exchange. Discover the mechanisms of tidal ventilation in lungs and specialized ventilation in birds. Explore the control of breathing and why the body senses carbon dioxide levels. Dive into the fascinating world of organismal respiration.

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Circulation and gas exchange II (Chapter 42)

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  1. Circulation and gas exchange II (Chapter 42)

  2. Fish gill Filaments Lamellae Tracheal system Tracheoles Gastrovascular cavity Lung Tidal ventilation Ventilation in birds Keywords

  3. Fish Gill

  4. Rather than being a solid structure, the fish gill is finely subdivided to enhance gas exchange area

  5. filaments

  6. lamellae Lamellae

  7. Countercurrent flow

  8. NOT countercurrent

  9. Countercurrent

  10. Are gills effective in increasing surface area? • 20 fold increase due to gills Surface area 1 kg 0.06 m2 Lime jello cube 1 kg 1.16 m2

  11. How do gill surface areas compare among different fishes? • Numbers correspond to arbitrary units per gram body weight

  12. Tracheal systems in insects

  13. Tracheoles supply tissues

  14. Diffusion distance from tracheole to mitochondria is short

  15. Lungs • Internal sacs • Unlike insect tracheal system lungs do not contact entire body • Circulatory system draws oxygen from lungs to tissues • Found in snails, a few fishes, spiders, vertebrates

  16. Structure of the mammalian lung

  17. Tidal ventilation of mammalian lung • Negative pressure breathing

  18. Tidal ventilation • Tidal volume - volume inhaled and exhaled (around 500 ml in humans) • Tidal volume is much less than total volume of lungs (several liters in humans) • Thus residual volume remains after exhaling • This is inefficient

  19. Birds have a more “sophisticated” type of lung ventilation • Birds have high metabolic rates • Can be exposed to lower oxygen concentrations in high altitude flight • Ventilation is not tidal • Air flows through the lungs

  20. The avian respiratory system

  21. The control of breathing • Human brain monitors carbon dioxide level (detected as a drop in blood pH) • Hyperventilation in divers • Diving mammals can tolerate high blood carbon dioxide

  22. Organismal respiration -- a simple view O2 O2 mitochondria CO2 CO2

  23. O2 CO2+H2O HCO3-+H+

  24. Why does the body sense carbon dioxide rather than oxygen? • Decreased oxygen corresponds to increased carbon dioxide • Increased carbon dioxide results in acidification which can readily be detected

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