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Chapter 44

Chapter 44. Gas Exchange. Respiration The exchange of gases between an organism and its environment Organismic respiration Takes place in animals O 2 taken up and CO 2 excreted Aerobic cellular respiration Takes place in mitochondria O 2 is necessary for citric acid cycle.

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Chapter 44

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  1. Chapter 44 Gas Exchange

  2. Respiration • The exchange of gases between an organism and its environment • Organismic respiration • Takes place in animals • O2 taken up and CO2 excreted • Aerobic cellular respiration • Takes place in mitochondria • O2 is necessary for citric acid cycle

  3. Simple diffusion • Passive movement of particles from a region of higher concentration to a region of lower • Provides gas exchange for small, aquatic organisms such as sponges, hydras, and flatworms

  4. Comparison of gas exchange in air and water • Air • Contains a higher concentration of molecular oxygen than water • Oxygen diffuses more rapidly through air than water • Less energy needed to move air over gas exchange surface

  5. Adaptations for gas exchange • Body surface • Small aquatic animals exchange gases by diffusion, requiring no specialized respiratory structures • Some invertebrates, including most annelids, and many amphibians exchanges gases across the body surface

  6. Gas exchange across body surface

  7. Adaptations for gas exchange, cont’d • Trachae • In insects and some other anthropods, air enters trachae through openings called spiracles • Trachae branch and extend to all regions of the body

  8. Gas exchange across tracheal tubes

  9. Adaptations for gas exchange, cont. • Gills • Moist, thin projections of the body surface found mainly in aquatic animals • Countercurrent exchange system maximizes O2 into the blood andCO2 out of the blood

  10. Gas exchange across gills

  11. Adaptations for gas exchange, cont. • Lungs • Terrestrial vertebrates have lungs and some means of ventilating them • Lungs are respiratory structures that develop as ingrowths of body surface or from wall of a body cavity

  12. Gas exchange across lungs

  13. Comparison of vertebrate lungs

  14. How bird lungs function

  15. Mammalian respiratory system • Includes the lungs and airways • Lung occupies pleural cavity and is covered with a pleural membrane • Breath of air passes in sequence • Nostrils, nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli

  16. The human respiratory system

  17. Structure of alveoli

  18. Mechanics of breathing • Diaphragm contracts and chest cavity expands • Respiratory centers in the medulla and pons regulate respiration • Stimulated by chemoreceptors • An increase in hydrogen ions and low oxygen concentration

  19. Mechanics of breathing

  20. Role of hemoglobin in oxygen transport • Respiratory pigment in vertebrate blood • Almost 99% of the O2 in human blood is transported as oxyhemoglobin (HbO2 )

  21. Gas exchange in the lungs and tissues

  22. Oxygen-carrying capacity • Maximum amount of O2 that can be transported by hemoglobin • Oxygen content • Actual amount of O2 bound to hemoglobin • Percent oxygensaturation • Ratio of O2 content to O2 carrying capacity

  23. Oxygen-hemoglobin dissociation curve • Shows that as O2 concentration increases, there is progressive increase in hemoglobin that combines with O2 • Bohr effect • Oxyhemoglobin dissociates more readily as CO2 increases

  24. Oxygen-hemoglobin dissociation curves

  25. Carbon dioxide transport

  26. Hyperventilation • Reduces the concentration of CO2 in the alveolar air and the blood • Decompression in divers • Rapid decrease in barometric pressure can cause decompression sickness • Diving mammals have high concentrations of myoglobin

  27. Deep diver

  28. Affects of pollution on the respiratory system • Ciliated mucous lining traps inhaled particles • Inhaling polluted air results in bronchial constriction • Increased mucous secretion • Damage to ciliated cells • Coughing

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