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Gas Exchange and Respiratory Systems

This chapter explores the process of gas exchange in organisms, focusing on respiratory adaptations and mechanisms in animals. Topics include comparisons of gas exchange in air and water, adaptations for gas exchange in different organisms, and the function and structure of respiratory systems such as gills, lungs, and the human respiratory system. The chapter also covers the transport of oxygen and carbon dioxide, the effects of pollution on the respiratory system, and the role of hemoglobin in oxygen transport.

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Gas Exchange and Respiratory Systems

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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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