Biology 2672a: Comparative Animal Physiology

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

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

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. 21.19 Fig. 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 Plecostomus - Gut Electric Eel - Mouth 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 Alveoli Alveolar duct Terminal Bronchiole Respiratory bronchiole 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. P1-P2 J=K X Ways to maximise O2 uptake • Countercurrent exchange • Reduce diffusion distance • Increase flow rate • Increase absorption of O2

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

19. The bird lung - orientation Anterior Air Sacs Anterior 2° bronchus Parabronchi Posterior 2° bronchus Posterior Air Sacs 1° bronchus Mesobronchus Beak Butt 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. P1-P2 J=K X Ways to maximise O2 uptake • Countercurrent exchange • Reduce diffusion distance • Increase flow rate • Increase absorption of O2

25. Bat lungs • Mammalian – alveolar dead space (etc) • ~Equivalent O2 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