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Gas Exchange

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  1. Gas Exchange Chapter 45

  2. Learning Objective 1 • Compare the advantages and disadvantages of air and water as mediums for gas exchange • Describe adaptations for gas exchange in air

  3. Gas Exchange in Air and Water • Air has a higher concentration of molecular oxygen than does water • Oxygen diffuses faster through air than through water • Air is less dense and less viscous than water (less energy needed to move air over gas exchange surface)

  4. Terrestrial Animals • Have adaptations that protect their respiratory surfaces from drying

  5. KEY CONCEPTS • Air has a higher concentration of molecular oxygen than water does, and animals require less energy to move air than to move water over a gas exchange surface • Adaptations in terrestrial animals protect their respiratory surfaces from drying

  6. Learning Objective 2 • Describe the following adaptations for gas exchange: body surface, tracheal tubes, gills, and lungs

  7. Adaptations for Gas Exchange 1 • Small aquatic animals • exchange gases by diffusion • no specialized respiratory structures • Some invertebrates (most annelids) and some vertebrates (many amphibians) • exchange gases across body surface

  8. Adaptations for Gas Exchange 2 • Insects and some other arthropods • air enters network of tracheal tubes (tracheae) through spiracles along body surface • tracheal tubes branch, extend to all body regions

  9. Tracheal Tubes

  10. Spiracle Tracheal tube (a) Location of spiral and tracheal tubes. Fig. 45-2a, p. 973

  11. Epithelial cell O2 Tracheal tube Tracheole Spiracle CO2 Muscle (b) Structure and function of a tracheal tube. Fig. 45-2b, p. 973

  12. Fig. 45-2c, p. 973

  13. Adaptations for Gas Exchange 3 • Aquatic animals have gills • thin projections of body surface • Chordates • gills usually internal, along edges of gill slits

  14. Adaptations for Gas Exchange 4 • Bony fishes • operculum protects gills • countercurrent exchange system maximizes diffusion of O2 into blood, CO2 out of blood • Animals carry on ventilation • actively move air or water over respiratory surfaces

  15. Gills in Bony Fishes

  16. Gill arch CO2 O2 Opercular chamber (a) Location of gills. Fig. 45-3a, p. 974

  17. Gill arch Blood vessels Gill filaments (b) Structure of a gill. Fig. 45-3b, p. 974

  18. Afferent blood vessel (low O2 concentration) Efferent blood vessel (rich in O2) (c) Countercurrent flow. Fig. 45-3c, p. 974

  19. Fig. 45-3d, p. 974

  20. Fig. 45-3e, p. 974

  21. Adaptations for Gas Exchange 5 • Terrestrial vertebrates have lungs • and some means of ventilating them • Amphibians and reptiles have lungs • with some ridges or folds that increase surface area

  22. Adaptations for Gas Exchange 6 • In birds • lungs have extensions (air sacs) that draw air into system • 2 cycles of inhalation and exhalation

  23. Gas Exchange in Birds • One-way flow of air through lungs • from outside into posterior air sacs, to lung, through anterior air sacs, out of body • Gas exchanged through walls of parabronchi • crosscurrent arrangement (blood flow at right angles to parabronchi) increases amount of O2 entering blood

  24. Gas Exchange in Birds

  25. Trachea Airsacs Air Lung Anterior air sacs Posterior air sacs (a) Structure of the bird respiratory system. (b) First inhalation. As the bird inhales, fresh air flows into the posterior air sacs (blue) and partly into the lungs (not shown). (c) First exhalation. As the bird exhales, air from the posterior air sacs is forced into the lungs. (d) Second inhalation. Air from the first breath moves into the anterior air sacs and partly into the lungs (not shown). Air from the second inhalation flows into the posterior air sacs (pink). (e) Second exhalation. Most of the air from the first inhalation leaves the body, and air from the second inhalation flows into the lungs. Fig. 45-5, p. 975

  26. Evolution of Vertebrate Lungs

  27. Trachea To other lung Salamander's lungs Frog's lungs Toad's lung Trachea To other lung Air sac Air sac Bird's lungs Reptile's lung Fig. 45-4, p. 975

  28. Adaptations for Gas Exchange

  29. Earthworm (a) Body surface. Fig. 45-1a, p. 972

  30. Grasshopper (b) Tracheal tubes. Fig. 45-1b, p. 972

  31. External gills Internal gills Gills Fish Mud puppy (c) Gills. Fig. 45-1c, p. 972

  32. Book lung Lungfish Spider Mammal (d) Lungs. Fig. 45-1d, p. 972

  33. Learn more about adaptations for gas exchange, including gills in bony fishes, vertebrate lungs, and the bird respiratory system, by clicking on the figures in ThomsonNOW.

  34. KEY CONCEPTS • Adaptations for gas exchange include a thin, moist body surface; gills in aquatic animals; and tracheal tubes and lungs in terrestrial animals

  35. Learning Objective 3 • Trace the passage of oxygen through the human respiratory system from nostrils to alveoli

  36. The Human Respiratory System • Includes lungs and system of airways • Each lung occupies a pleural cavity and is covered with a pleural membrane • Air passes through nostrils, nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, alveoli

  37. The Human Respiratory System

  38. Sinuses Respiratory centers Nasal cavity Tongue Epiglottis Pharynx Larynx Esophagus Trachea Bronchioles Space occupied by heart Bronchus Right lung Left lung Diaphragm Fig. 45-6, p. 976

  39. Structure of Alveoli

  40. Capillary Red blood cells Bronchiole Macrophage Alveolus Capillaries Alveolus Alveolus Epithelial cell of the wall of the alveolus Epithelial cell of the adjacent alveolus (a) Fig. 45-7a, p. 977

  41. Fig. 45-7b, p. 977

  42. Wall of alveolus Red blood cell Wall of capillary 1 µm (c) Fig. 45-7c, p. 977

  43. Insert “Human respiratory system” human_respiratory_v2.swf

  44. Learn more about the human respiratory system by clicking on the figures in ThomsonNOW.

  45. Learning Objective 4 • Summarize the mechanics and the regulation of breathing in humans • Describe gas exchange in the lungs and tissues

  46. Mechanics of Breathing • Diaphragm contracts • expanding chest cavity • Membranous walls of lungs move outward along with chest walls • lowering pressure within lungs • Air rushes in through air passageways • until pressure in lungs equals atmospheric pressure

  47. Mechanics of Breathing

  48. Trachea Lung Diaphragm (a) Inhalation. (b) Exhalation. Fig. 45-8ab, p. 978

  49. Diaphragm (c) Forced inhalation. (d) Forced exhalation. Fig. 45-8cd, p. 978

  50. Respiratory Measurements • Tidal volume • amount of air moved into and out of lungs with each normal breath • Vital capacity • maximum volume exhaled after lungs fill to maximum extent • Residual capacity • air volume remaining in lungs at end of normal expiration