1. Biology 2672a: Comparative Animal Physiology Breathing in air

2. Gas transport in organisms - a combination of convection and diffusion Tidal convection ventilates lungs Diffusion into bloodstream Unidirectional flow (convection) in circulatory system Diffusion from capillaries into tissues

3. Concurrent gas exchange Fig. 21.4a

4. Countercurrent gas exchange Concurrent Fig 21.4b

5. Countercurrent gas exchange Concurrent Fig 21.4b

6. Cross-current gas exchange Fig. 21.5

7. Mammal lungs are inefficient Fig. 21.19Fig. 21.3

8. Breathing Air  Lots of Oxygen!  Not so easy to get rid of CO2  Problems with water loss  Lungs (invaginations)

9. (Most) Fishes Breathing Air Electric Eel - Mouth Plecostomus - Gut Bowfin – Swim bladder Fig. 23.15

10. Tracheal system Fig. 22.29

11. Construction of the tracheal system  A branched series of tubes that are filled with air (except at the very ends)  Trachea>Tracheoles  Terminal tracheoles Constructed from a single invaginated cell Distance between lumen & cell = 3 x cell membranes Fluid-filled

12. Tracheal system  Very extensive no cell is more than 2-3 cell diameters from a tracheole Tissues with high metabolism (e.g. flight muscle) may have at least one terminal tracheole penetrating each cell (!) On-tap oxygen in every cell!

13. Gas transport in the tracheal system  Diffusion works very well in gases  Some convection Thorax & abdomen pumping Caused by partial pressure gradients? Tracheal pumping? (see movie on WebCT)  One-way flow systems  ‘Ram’ ventilation (draft ventilation)

14. Mammal lungs Trachea Bronchus Terminal Bronchiole Respiratory bronchiole Alveolar duct Alveoli Fig. 21.18

15. Breathing air while flying  Energetic costs of flying are 2.5- 3 × higher than running  Two groups of extant flying vertebrates

16. Insects -Tracheal system reaches every cell

17. Ways to maximise O 2 uptake  Countercurrent exchange  Reduce diffusion distance  Increase flow rate  Increase absorption of O 2 J=K P 1 -P 2 X

18. Bird lungs – a one-way system Fig. 22.24

19. The bird lung - orientation Beak Butt Anterior Air Sacs Posterior Air Sacs 1° bronchusMesobronchus Parabronchi Posterior 2° bronchus Anterior 2° bronchus Fig. 22.22

20. Bird lung: Breathe in

21. Bird lung: Breathe Out See also Fig 22.22

22. Bird Lungs: Gas-blood  Highly efficient >37 % of O2 extracted from the air  Mammals: ~25%  Thin blood-gas barriers  Surface area : body size ~ same as mammals  Surface area : lung volume ~2× mammals

23. Bird Lungs: Cross-current gas exchange Fig. 22.23c Fig. 22.5

24. Ways to maximise O 2 uptake  Countercurrent exchange  Reduce diffusion distance  Increase flow rate  Increase absorption of O 2 J=K P 1 -P 2 X

25. Bat lungs  Mammalian – alveolar dead space (etc)  ~Equivalent O 2 uptake to birds  Heart size, Heart output   Haematocrit  Large lungs Surface area pulmonary blood volume thickness of blood-gas barrier

26. Bats vs birds  Largest birds (~18 kg) much larger than largest bats (~1.5 kg)  Birds function perfectly well (fly!) at high altitude Geese over Mt Everest Vulture in jet engine at 11.2 km High altitude climbers not plagued with bats…

27. Reading for Thursday  Blood  Pp581-603