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Gas exchange

Gas exchange. Key concepts. Gas exchange occurs across specialized respiratory surfaces Gills in aquatic animals Tracheal systems in insects Lungs Breathing ventilates the lungs Amphibian breathing Bird breathing Control of breathing in humans

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Gas exchange

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  1. Gas exchange

  2. Key concepts • Gas exchange occurs across specialized respiratory surfaces • Gills in aquatic animals • Tracheal systems in insects • Lungs • Breathing ventilates the lungs • Amphibian breathing • Bird breathing • Control of breathing in humans • Respiratory pigments bind and transport gases • Diffusion and partial pressure • Respiratory pigments • O2 and CO2 transport

  3. Vocabulary words • ventilation • lungs • vocal cords • bronchioles • diaphragm • residual volume • respiratory pigments • Bohr shift • countercurrent exchange • gills • trachea • alveoli (alveolus) • tidal volume • breathing control centers • hemoglobin • carbon dioxide transport • respiratory surface • tracheal system • larynx • bronchi (bronchus) • breathing • vital capacity • partial pressure • dissociation curve for hemoglobin

  4. Respiratory surfaces and gas exchange • Gas exchange – uptake of O2 from environment and discharge of CO2 • Mitochondria need O2 to produce more ATP, CO2 is the by-product C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP • Diffusion rate • α SA  large • α 1/d2  thin • Moist so gases are dissolved first DIFFUSION

  5. Respiratory surfaces and gas exchange • Respiratory surface • Size of organism • Habitat • Metabolic demands • Unicellular organisms • Entire surface area for diffusion • Simple invertebrates • Sponges, cnidarians, flatworms • diffusion

  6. Respiratory surfaces and gas exchange • More complex animals • Thin, moist epithelium • Separates medium from capillaries • Entire outer skin small, long, thin organisms • Specialized respiratory organs that are extensively folded and branched

  7. Gills in aquatic animals • Outfoldings of the body surface suspended in water • Sea stars • Segmented worms or polychaetes • Molluscs and crustaceans • Fishes • Young amphibians • Total surface area is greater than the rest of the body

  8. Water as a respiratory medium Just keep swimming swimmingswimming! • Surfaces are kept moist • O2 concentrations in water are low • Ventilation – increasing flow of respiratory medium over the surface • Countercurrent exchange – process in which two fluids flow in opposite directions, maximizing transfer rates • Why are gills impractical for land animals?

  9. Air as a respiratory medium • Air has a higher concentration of O2 • O2 and CO2 diffuse much faster in the air  less ventilation • Difficulty of keeping surface moist • Solution: respiratory infolding inside the body • Tracheal system of insects – network of tubes that bring O2 to every cell Spiracles

  10. Lungs • Heavy vascularized invaginations of the body surface restricted to one location • Found in spiders, terrestrial snails, vertebrates • Amphibians supplement lung breathing with skin • Turtles supplement lung breathing with moist surfaces in mouth and anus

  11. Mammalian respiration

  12. Lung ventilation through breathing • Positive pressure breathing in frogs • “Gulping in” air • Negative pressure breathing in reptiles and mammals • Rib muscles and diaphragm change lung volume and pressure

  13. Lung volumes • Factors • Sex • Height • Smoking • Physical activity • Altitude • Tidal volume • Volume of air inhaled and exhaled with each breath • Vital capacity • Maximum volume inhaled and exhaled during forced breathing • Residual volume • Air left in alveoli after forced exhalation

  14. Avian breathing Air sacs act as bellows to keep air flowing through the lungs.

  15. Control centers in the brain regulate breathing

  16. Gases diffuse down pressure gradientsconcentration and pressure drives the movement of gases into and out of blood

  17. Respiratory pigments • O2 transport • Low solubility of O2 in H2O • Respiratory pigments are proteins with metal atoms • Hemoglobin – Fe • Hemocyanin – Cu • Allow reversible binding of O2 • Drop in pH results in a lowered affinity of hemoglobin for O2

  18. Respiratory pigments • CO2 transport • 7% in plasma • 23% bound to hemoglobin • 70% as HCO3- • buffer

  19. Fetal hemoglobin HbF has greater affinity to O2 than Hb • low O2% by time blood reaches placenta • fetal Hb must be able to bind O2 with greater attraction than maternal Hb

  20. Deep-diving mammals • Seals, whales, dolphins are capable of long underwater dives • Weddell seal  5% O2 in lungs, 70% in blood • Huge spleen stores huge volumes of blood • Large concentrations of myoglobin in muscles • Heart rate and O2 consumption rate decrease • Blood is redirected from muscles to brain spinal cord and eyes

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