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Gas Exchange and Respiratory Surfaces in Animals

Learn how gas exchange occurs across specialized respiratory surfaces, supplying oxygen for cellular respiration and disposing of carbon dioxide. Explore the importance of surface-to-volume ratio in gas and heat exchange at organismal and cellular levels. Discover unique respiratory adaptations in animals at different sizes.

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Gas Exchange and Respiratory Surfaces in Animals

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  1. Chapter 42 Circulation and Gas Exchange

  2. Concept 42.5: Gas exchange occurs across specialized respiratory surfaces • Gas exchange supplies oxygen for cellular respiration and disposes of carbon dioxide • Animals require large, moist respiratory surfacesfor adequate diffusion of gases between their cells and the respiratory medium, either air or water

  3. Respiratory medium (air or water) Respiratory surface O2 CO2 Organismal level LE 42-19 Circulatory system Cellular level Energy-rich fuel molecules from food ATP Cellular respiration

  4. Tissue cell INTERSTITIAL or EXTRACELLULAR FLUID Net fluid movement out Net fluid movement in Capillary LE 42-14 Capillary Red blood cell 15 µm Direction of blood flow Blood pressure Osmotic pressure Inward flow Pressure Outward flow Arterial end of capillary Venous end

  5. Surface-to-Volume Ratio • The rate at which an organism can absorb O2 or give off CO2 depends on its surface area • Need determined by volume

  6. Surface-to-Volume Ratio • The bigger the organism gets, its need for oxygen grows faster than its ability to supply that need. • SOLUTION: CREATE MORE SURFACE AREA!

  7. Proportional to SURFACE Proportional to VOLUME O2 use; CO2 produced Big = more O2 use Heat production Big = more heat production Weight of an organism • Rate of gas exchange • Rate of heat exchange (or heat loss) • Strength of limb • More muscle, greater strength • Friction on an organism Different adaptations  accommodate different needs

  8. Surface-to-Volume Ratio • Homeothermic Animals • Maintain body temp slightly higher than environment • Constantly lose heat • Heat produced depends on volume • Smaller = greater S/V ratio • More surface area to lose heat • So… smaller organism means it loses more heat • Must make it up by metabolizing more  eat more

  9. Consider this graph… metabolic rate Volume O2 needed Body mass unit time metabolic rate Heat loss elephant mouse Surface to volume ratio

  10. Respiratory Surfaces

  11. Body Surface • Gastrovascular cavities • Used by very small, cold-blooded animals • Planaria, protozoa, sponges, cnidaria

  12. Gills in Aquatic Animals • Gills are outfoldingsof the body surface specialized for gas exchange

  13. In some invertebrates, gills have a simple shape and are distributed over much of the body Gills Coelom Tube foot

  14. Many segmented worms have flaplike gills that extend from each segment of their body Parapodia Gill

  15. The gills of clams, crayfish, and many other animals are restricted to a local body region Gills

  16. LE 42-20d Gills Crayfish

  17. Problem: water is too dense and can take a lot of energy to move • Solution: Effectiveness of gas exchange in some gills, including those of fishes, is increased by ventilation and the countercurrent flow of blood and water

  18. Oxygen-poor blood Lamella Oxygen-rich blood Gill arch LE 42-21 Blood vessel Gill arch 15% 40% 70% Water flow 5% 30% Operculum 60% 100% 90% Water flow over lamellae showing % O2 O2 Blood flow through capillaries in lamellae showing % O2 Gill filaments Countercurrent exchange

  19. Oxygen-poor blood Lamella Oxygen-rich blood 15% 40% 70% 5% 30% 100% 60% 90% Water flow over lamellae showing % O2 O2 Blood flow through capillaries in lamellae showing % O2 Countercurrent exchange

  20. Tracheal Systems in Insects • The tracheal system of insects consists of tiny branching tubes that penetrate the body Tracheae Air sacs Spiracle

  21. Body cell Air sac Tracheole LE 42-22b Trachea Air Body wall Mitochondria Tracheoles Myofibrils 2.5 µm

  22. Lungs • Spiders, land snails, and most terrestrial vertebrates have internal lungs

  23. Mammalian Respiratory Systems: A Closer Look • A system of branching ducts conveys air to the lungs • Pathway of air • Air inhaled through the nostrils passes through the pharynx into the trachea, bronchi, bronchioles, and dead-end alveoli, where gas exchange occurs

  24. Branch from Pulmonary artery (oxygen-poor blood) Branch from pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity Pharynx Alveoli Larynx Left lung 50 µm Trachea Right lung 50 µm Bronchus Bronchiole Colorized SEM SEM

  25. Epiglottis Esophagus Pleural membranes (pleurae) Diaphragm

  26. Concept 42.6: Breathing ventilates the lungs • The process that ventilates the lungs is breathing, the alternate inhalation (inspiration) and exhalation (expiration) of air

  27. How an Amphibian Breathes • An amphibian such as a frog ventilates its lungs by positive pressure breathing, which forces air down the trachea

  28. How a Mammal Breathes • Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs • Lung volume increases as the rib muscles and diaphragm contract

  29. Rib cage gets smaller as rib muscles relax Rib cage expands as rib muscles contract Air inhaled Air exhaled Lung Diaphragm INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up)

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