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Fick's law of diffusion
- Q = DA(P1 - P2)/L
- Q - the rate at which a substance diffuses between two location
- D - the diffusion coefficient, dependent on size and shape of diffusing substance, medium, and temperature
- A - the cross sectional area over which the substance is diffusing
- P1, P2 - the partial pressure of the gas at two locations
- L - is the disance between these locations
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Adaptions for maximizing respiratory gas exchange
- Increase the surface area of exchange
- maximize the partial pressure gradient
- Proper ventilation of the respiratory medium
- Proper blood flow on the inside of the respiriatory suface
- Decrease distance between the two sides of the medium
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Air vs. Water breathing
- Easier to obtain O2 from air than water
- Air contains 20x more O2
- O2 diffuses 8,000 times more rapidyly
- Water breathers must work harder to breathe than air breathers
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Temperature Effects on O2 in water
- As temperatures rise, so does the animal's metabolism and the need for more O2
- Warm water holds less O2 than cold water
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O2 Diffussion in the Organism
- Because of the slow diffusion of O2 in water, the PPO2 of cells has to be 1-2mm Hg
- Animals w/o internal transport of O2 are either severly limited in size or have evolved bodies that are flattened or built around a central cavity
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Tracheae
branched tubules in insects used for gas exchange
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Gas exchange system
Gas exchange surface + the mechanisms used to ventilate and perfuse gas exchange surface
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Spiracles
tracheae openings to the outside world
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Tracheoles
branches of the tracheae in insects where O2 is delviered to air capillaries very close to cell mitochondria
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Gas Gill/ Plastron
Bubble of air used by insects for breathing underwater
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Hydrofuge
numerous cuticular hairs on the surface of an insect to maintain a constant gas gill
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Gas exchange for fish
- Gills have high surface area
- Double pump system for ventilation (mouth and operculum)
- Constant one-way water flow over the gills maximizes PO2 on the external gill surface
- Counter-current blood flow maximizes O2 exchanged.
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lamellae
gas exchange surface for gills
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Gill arch
break into gill filaments with lamella on the filaments
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Aviary Respiration
- Air flows unidirectionally through lungs to maximize gradients
- Air sacs connect to lungs to allow for unidirectional flow
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Parabronchi
further subdivizion of bronchi in birds that run parallel to one another
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Alligator respiration
- One-way air flow but no air sacs
- Mechanism unknown
- Reminder: birds and crocodilians evolved from DINOSAURS RAWRRRR!
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Tidal volume
amount of air exchanged in a single breath at rest
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Vital capacity
maximum usable lung volume
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Anatomical dead space
- airways in which gas exchange cannot occur.
- Residual volume is the air that keeps the lungs from collapsing, part of the dead space
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Total lung capacity
residual volume + vital capacity
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How are the ineffeciencies of tidal breathing compensated in mammalian lungs
- Enormous surface area
- Short path length for diffusion
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Surfactant (lipoproteins)
A chemical substance that reduces the surface tension of a liquid
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Respiratory Stress Syndrome
- Possible in premaure babies
- Alveoli don't produce surfactants yet
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Intercostal muscle (internal/external)
lift ribgs up or down to increase thoraic cavity
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