BIOL125 Lecture Notes - Lecture 11: Acidosis, Blood Plasma, Peripheral Chemoreceptors
BIOL week 11 LB Gas Exchange and Gas Transport
Respiration
- The process that provides the body’s cells with O2 and removes the waste product
CO2
- Respiration includes five separate processes:
1. Pulmonary ventilation
oMovement of air in and out of the lungs
2. External respiration (pulmonary gas exchange)
oGas exchange between alveolar air and blood
3. Gas transport
oTransport of O2 and CO2 in blood
4. Internal respiration (tissue gas exchange)
oGas exchange between blood and tissues/cells
5. Cellular respiration
oThe process of oxidising food molecules to CO2 and water
Dalton’s Law
- Pulmonary and tissue gas exchange
oExternal and internal respiration, respectively
- Dalton’s law of partial pressure (1801)
oIn a mixture of gases, each gas exerts its own pressure
- Partial pressure
oTotal gas pressure: sum of all individual pressures
oPN2 + PO2 + Pothers = Atmospheric pressure (760 mmHg)
oPN2 = 0.78 x 760 mmHg = 593 mmHg
oPO2 = 0.21 x 760 mmHg = 160 mmHg
Alveolar Air
- The composition of air we breathe in and the composition of air in our alveoli are not
the same thing
- Consider this – in an average person, only 350 mL (of 2,650 mL) gets replaced by new
atmospheric air after each respiratory cycle
Alveolar versus Atmospheric Air
O2CO2H2O
Atmospheric air 160 mmHg 0.3 mmHg 3.7 mmHg
Alveolar air 104 mmHg 40 mmHg 47 mmHg
- Alveolar air is very different to atmospheric air
- O2 is lower in alveoli (alveolar air)
- CO2 is much higher in alveoli
- Alveolar air is humidified
So alveolar air and atmospheric air are different this is a good thing
- The composition of alveolar air is fairly constant, therefore
- There are no sudden changes in the gas concentrations of the blood even if you hold
your breath or hyperventilate
- Which means that there are no excessive decreases or increases in tissue
oxygenation, tissue CO2 concentration, and tissue pH (for a while)
External Respiration
- O2 moves from the alveoli into the blood
- CO2 moves from the blood into the alveoli
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- Simple diffusion across the respiratory membrane moves across pressure gradient
- The rate of diffusion depends on:
oPartial pressure difference
oSurface area available for diffusion
oThickness of the respiratory membrane
Surface Area
- The total surface area of the respiratory membrane is at least 70 m2
- The total quantity of blood in the capillaries of the lungs at any given instant is 60-
140 mL
oThe volume of standard shot cups in Australia is 30 mL
Alveolar Wall
- Type I alveolar cells/pneumocytes
oSquamous, extremely thin cells
oProvide 90% of the wall surface
- Type II alveolar cells/pneumocytes
oCuboidal cells
oProvide 5-10% of wall surface
oBut represent about 60% of the epithelial cells in the alveoli
oProduce surfactant
- Alveolar macrophages
oCleaning (‘dust cells’)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Biol week 11 lb gas exchange and gas transport. The process that provides the body"s cells with o2 and removes the waste product. Respiration includes five separate processes: pulmonary ventilation, movement of air in and out of the lungs, external respiration (pulmonary gas exchange, gas exchange between alveolar air and blood, gas transport. 4: transport of o2 and co2 in blood. Internal respiration (tissue gas exchange: gas exchange between blood and tissues/cells, cellular respiration, the process of oxidising food molecules to co2 and water. Pulmonary and tissue gas exchange: external and internal respiration, respectively. Dalton"s law of partial pressure (1801: in a mixture of gases, each gas exerts its own pressure. Partial pressure: total gas pressure: sum of all individual pressures, pn2 + po2 + pothers = atmospheric pressure (760 mmhg, pn2 = 0. 78 x 760 mmhg = 593 mmhg, po2 = 0. 21 x 760 mmhg = 160 mmhg.
