Lecture 59 - Gas Exchange and Transport Flashcards
(53 cards)
How much is 1 atm?
760 mmHg
Describe relative gas concentrations in the air
Nitrogen: high partial pressure
Oxygen: 160 mmHg
CO2: very low partial pressure
What is the difference between reidual and reserve volume?
Residual: can never be expirated
Reserve: amount that can be exhaled
Why have a residual volume?
- decreases energy required to reinflate lungs
- lung would not remain open
What happens to dead space during exercise?
nothing
Remains the same
Describe the features of the alveoli that make it good for gas exchange
- large surface area
- very thin wall to diffuse across
Describe the structures that oxygen moves across to get into the blood
One cell thick alveolar epithelium
Fused basement membrane
Endothelial cell
How does Fick’s law relate to alveolar structure?
Fick’s law of diffusion says;
- increased surface area
- decreased thickness
- greater pressure gradient
will lead to greater rate of diffusion of oxygen across the alveoli
Describe how concentration of gases in the atmosphere changes with altitude
The concentration does vary very much
It is the partial pressures of the gases that changes
Which variables can be altered to increase rate of diffusion of oxygen into the blood?
Concentration of oxygen in the breathed air
eg in Anaesthesia
65% oxygen in air
Describe what happens to the partial pressure of oxygen when air moves from the atmosphere into the alveoli
Why?
Partial pressure drops; 160 –> 100 mmHg
- mixing with old air with depleted oxygen
- air is moistened by mucous membrane
Compare the differences in PO2 in oxygenated and deoxygenated blood
Oxygenated: 100 mmHg
Deoxygenated: 40 mmHg
What happens to oxygen when we climb up higher than 5 km?
PO2 drops to 80 mmHg
Less oxygen is getting into the blood
Describe gases dissolving into liquids
When a liquid is exposed to a gas at a given pressure, the gas will move into solution until…
Partial pressure of gas is the same in the liquid and in the air.
How does solubility affect dissolution of gases into liquids?
Greater solubility:
- greater concentration of the gas in the liquid once equilibrium is reached
eg. CO2
Lesser solubility:
- lesser concentration of gas in the liquid once equilibrium is reached
eg O2
At equilibrium, will the concentration of the gas in the liquid and in the air be the same?
No
This depends on solubility of the gas
Is O2 or CO2 more soluble?
CO2
Describe how oxygen is transported in the blood
- O2 diffuses through cells into plasma
2. Combines chemically with haemoglobin (Hb)
Why must oxygen combine with Hb in the blood?
Because O2 is very insoluble
Hb increases the oxygen carrying capacity of the blood
How much Hb is present in the body?
Males: 15g / 100 ml
Females: 13g / 100 ml
What is the concentration of oxygen in the blood?
173 ml / L of blood
What is VO2 max?
The maximum amount of oxygen that can be taken up from the environment per unit time
What measurement is a good measure of fitness?
VO2 max
ie amount of oxygen that can be carried
How can VO2 max be increased?
EPO
