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Transcript
Biology 2672a: Comparative Animal Physiology Breathing in air Gas transport in organisms - a combination of convection and diffusion Tidal convection ventilates lungs Unidirectional flow (convection) in circulatory system Diffusion from capillaries into tissues Diffusion into bloodstream Concurrent gas exchange Fig. 21.4a Countercurrent gas exchange Concurrent Fig 21.4b Countercurrent gas exchange Concurrent Fig 21.4b Cross-current gas exchange Fig. 21.5 Mammal lungs are inefficient Fig. 21.19 Fig. 21.3 Breathing Air Lots of Oxygen! Not so easy to get rid of CO2 Problems with water loss Lungs (invaginations) (Most) Fishes Breathing Air Plecostomus - Gut Electric Eel - Mouth Bowfin – Swim bladder Fig. 23.15 Tracheal system Fig. 22.29 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 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! 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) Mammal lungs Trachea Bronchus Alveoli Alveolar duct Terminal Bronchiole Respiratory bronchiole Fig. 21.18 Breathing air while flying Energetic costs of flying are 2.53 × higher than running Two groups of extant flying vertebrates Insects -Tracheal system reaches every cell Ways to maximise O2 uptake Countercurrent exchange Reduce diffusion distance Increase flow rate Increase absorption of O2 J=K P1-P2 X Bird lungs – a one-way system Fig. 22.24 The bird lung - orientation Anterior Air Sacs Beak 1° bronchus Mesobronchus Posterior Air Sacs Butt Fig. 22.22 Bird lung: Breathe in Bird lung: Breathe Out See also Fig 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 Bird Lungs: Cross-current gas exchange Fig. 22.23c Fig. 22.5 Ways to maximise O2 uptake Countercurrent exchange Reduce diffusion distance Increase flow rate Increase absorption of O2 J=K P1-P2 X 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 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… Reading for Thursday Blood Pp581-603
