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Circulation and Gas Exchange

This text discusses the different types of circulation systems in organisms, from direct exchange in single-celled organisms to closed circulatory systems in vertebrates. It also explores the various respiratory surfaces and mechanisms of gas exchange.

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Circulation and Gas Exchange

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  1. Ch 42 Notes Circulation and Gas Exchange

  2. Circulation Used to get nutrients and Oxygen in through cell membranes and waste products out through same cell membrane Direct Exchange – Occurs in single celled organisms, sponges Gases and nutrients move directly from environment into and out of cells

  3. Gastrovascular Cavity • Single Opening – Only 2 cell layers in body • Inner and Outer Tissue bathed by fluid • Nutrients, Gases and Waste move by diffusion • Cnidarians, Planarians/Flatworms

  4. Circulatory System • Animals with many cell layers • Fluid transported in Circulatory System connected to body cells • 3 Parts to System • Circulatory Fluid • Interconnecting Tubes • Muscular Heart to Pump

  5. Open Circulatory System • Circulatory fluid bathes organs directly (no vessels) • Fluid called Hemolymph • Heart (s) pump hemolymph through vessels into sinuses surrounding organs • Chemical exchange occurs • Don’t need much energy • Arthropods, mollusks

  6. Closed Circulatory System • Fluid (blood) confined to vessels • Blood is separate from interstitial fluid (fluid that surrounds cells) • One or more hearts pumps blood into large vessels, leads to smaller vessels, then to cells • Allows for higher activity levels • Annelids, Cephalopods (squid/octopus) and all Vertebrates

  7. Vertebrate Circulatory Systems • Cardiovascular System • Extensive network of vessels • Arteries - carry blood away from heart (arterioles – small arteries) • Capillaries – tiniest vessels (one cell layer thick) where exchange of gas and nutrients occurs – right next to cells • Veins – bring blood back to heart (venule – small vein)

  8. Single Circulation • 2 – chambered heart • One atrium and one ventricle • Blood enters heart through atrium, moves into ventricle, pumped to gills (Oxygen into blood, CO2 out, Artery carries blood to body cells, vein returns it to heart • Fish, Sharks, Rays

  9. Double Circulation • Heart has 2 pumps for coordination • Right side – Pulmonary Circuit – Oxygen poor blood goes to gas exchange tissue (lungs) and gets O2 and gets rid of CO2 • Blood returns to Left side of heart – Systemic Circuit – gets pumped to the rest of body through arteries – capillaries (oxygen and nutrients given to cells, waste picked up) and returns to right side through veins

  10. Amphibians • Three chambered Heart – 2 atria and one ventricle • Get some mixing of blood with and without oxygen • Gas exchanged through both skin and lungs

  11. Reptiles • Three chambered heart with septum partially dividing the ventricle • Better separation of blood with and without oxygen

  12. Mammals and Birds • 4 Chambered Heart – 2 atria, 2 ventricles • Complete separation of blood with and without oxygen • Allows them to be endothermic because the heart is more efficient at delivering oxygen and fuel to cells

  13. Mammalian Circulation Right Atrium Tricuspid Valve Right Ventricle Pulmonary Semilunar Valve Pulmonary Artery Lungs (pick up Oxygen, release Carbon Dioxide Pulmonary Vein Left Atrium Bicuspid Valve Left Ventricle Aortic Semilunar Valve Aorta Arteries Arterioles Capillaries (give Oxygen and nutrients to cells, pick up waste) Venules Veins Vena Cava Start over

  14. Gas Exchange • Uptake of Molecular Oxygen and discharge of Carbon Dioxide • Can be through air (easier) or water (more difficult) • Warmer/Saltier water holds less oxygen than fresh water

  15. Respiratory Surfaces • Always Moist • Exchange occurs by Diffusion • Exchange is fast when area for diffusion is large and surface is thin • Sponges/Cnidarians – direct gas exchange • Earthworms/Some Amphibs – thru skin • Aquatic Vertebrates – Gills • Insects – Tracheal Tube system • Terrestrial Vertebrates - Lungs

  16. Alveoli • Site of Gas Exchange in Mammals • Millions inside each lung • Large Surface Area • Found close to capillaries to make gas exchange easier

  17. Breathing - Mammals • Use Negative Pressure – pulls air in • Diaphragm – Muscle beneath lungs • Diaphragm Contracts • Thoracic cavity increase (pressure decreases) • air pulled in (inhalation) • Diaphragm relaxes • Thoracic cavity decreases (pressure increases) • air pushed out (exhalation)

  18. Control Of Breathing • Medulla Oblongata (in brain) – sets rhythm of breathing • Pons (in brain) – controls inhale/exhale tempo • CO2 concentration changes the pH of blood which signals to the medulla how fast breathing should occur • More CO2 = lower pH = faster breathing • Less CO2 = higher pH = slower breathing

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