Respiratory Systems and gas exchange

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Respiratory Systems and gas exchange

• Chapter 9

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Cellular Respiration

• C6H1206 6O2 ---gt 6CO2 6H20
• CO2 H20lt---gtH2CO3 lt---gtHCO3- H
• Carbonic acid bicarbonate

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Composition of the atmosphere

• Total air pressure 100
• N2 78
• O2 21
• Ar 1
• CO2 0.03 (and rising!)
• Others lt1
• Proportions constant

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• The weight of the atmosphere
• Measured in
• mm Hg (Mercury)

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Daltons Law of Partial Pressures

• Total Pressure 100 760mm Hg
• N2 78 592mm Hg
• O2 21 159mm Hg
• Argon 1 7.6mm Hg
• CO2 0.03 0.23mm Hg
• Others lt1 2mm Hg
• Partial Pressures change with altitude

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Respiration strategies depend on demand
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All have moist surfaces for gas exchange
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Ficks Law of diffusion

• RDA (DP/d)
• R Rate of diffusion
• D Diffusion constant (0 to 1)
• A Area for diffusion
• DP Difference in concentration
• d distance

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Relationship between surface area and volume
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O2 requirements

• FO2 VO2 r2 x 760
• k
• FO2 Required O2 at membrane (mmHg)
• VO2 O2 consumption rate (0.001 ml/g tissue/min)
• r radius
• k Diffusion coefficient (6.6x10-5 ml
  O2/cm2/min/atm)

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Effect of size

• 1cm radius
• 0.1cm radius

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Effect of size

• 1cm radius
• 0.001 x 12 x 760 11400 mm Hg
• 6.6 x 10-5
• 0.1cm radius
• 0.001 x 0.12 x 760 114mm Hg
• 6.6 x 10-5

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Factors affecting respiration

• In air
• In water
• Amount of gas dissolved in water in equilibrium
  with amount of gas above water surface

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Gasses in water-Henrys Law of dissolved gases

• V aP
• V Volume of dissolved gas (ml/L) G
• a Bunsen solubility coefficient (varies with
  temperature and other solutes) S gas
• P Partial Pressure of gas (mmHg) Pgas

G Pgas x S gas
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Gas solubility

• 15oC- 1atm (760mmHg) gas above pure water surface

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Oxygen dissolved in water

• Gases are less soluble in water at higher
  temperatures
• Oxygen in air 209ml/l

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O2 content in air and water

• Water in equilibrium with air at 15oC contains
  7ml (10mg) O2 per liter (106mg)
• Move 100,000 x weight
• Air contains 209ml (280mg) O2 per liter (910mg)
• Move 3.5 x weight

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• Tidal vs. unidirectional flow

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Roles of the Respiratory System

• Provides a means of gas exchange between the
  environment and the body
• Plays a role in the regulation of acid-base
  balance during exercise
• Provides varying amounts of O2 depending upon
  activity level
• Must cope as well as possible with changes in O2
  availability

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Effects of orientation of the flow of the
external medium and the blood on gas exchange
efficiency-Part 1
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Effects of orientation of the flow of the
external medium and the blood on gas exchange
efficiency-Part 2
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Aquatic Organisms
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Molluscs
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Lamprey
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Hagfish and Lamprey
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Elasmobranchs
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Teleost fish
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Concurrent exchange Blood and water both move in
same direction Hypothetically, this would allow
50 exchange Does not occur in fish
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Countercurrent exchange Blood and water move in
opposite directions through the gills Allows for
more efficient acquisition of O2 from water Saves
energy! Unidirectional flow
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Air-breathing fish
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• C6H1206 6O2 ---gt 6CO2 6H20

• V?P
• PV/?

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Gas solubilities

• 15oC- 1atm gas above pure water surface

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Lungfish Obligate and facultative