6 Haemoglobin & Gas transport Flashcards
How much Oxygen is dissolved in every litre of plasma?
3ml
What is the oxygen carrying capacity of the blood?
200 ml/L
What determines the arterial partial pressure of O2?
The oxygen dissolved in the blood
NOT the oxygen carried by haemoglobin
What 2 factors influence how much O2 is dissolved?
- Its solubility
- The partial pressure of gaseous oxygen driving the O2 into solution (basically the partial pressure in the alveoli)
What is the patial pressure of the oxygen in solution?
100mmHg (sometimes called oxygen tension)
Its equal to the PO2 driving it across.
What is the oxygen demand of resting cells?
250ml/min
What is cardiac output?
Around 5L/min
How much haemoglobin is in the average person?
150g/L
How much oxygen is carried in every gram of haemoglobin?
1.34ml of O2 per gram of haemoglobin
How much oxygen is carried in the haemoglobin of a normal person?
[150g haemoglobin/L]
[5L/min cardiac output]
[1.34ml O2/g of haemoglobin]
5 litres every minute
-> 5L x 150g = 750g/min
- 34ml O2/g
- > 750 x 1.34 = 1000ml/min
How much of the arterial O2 is extracted by tissue at rest?
Only about 25%
Since resting tissues use 250ml/min and haemoglobin carries 1000ml/min
How is the PO2 gradient maintained betweent the blood & alveoli?
Haemoglobin takes up arterial oxygen so the gradient doesnt reach equilibrium
What is the most common form of Haemoglobin? Descibe?
HbA
Makes up 92% of haemoglobin
Made up of 2 alpha & 2 beta chains
What are some other types of haemoglobin?
HbA2
HbF (Foetal)
Glycosylated Hb
myoglobin
What makes up foetal haemoglobin?
2 Alpha chains
2 Gamma chains
What makes up HbA2?
2 Alpha chains
2 Delta chains
What are the types of glycosylated Hb?
HbA1a
HbA1b
HbA1c
Where is myoglobin found?
In oxidative muscle fibres
How does a foetus extract O2 from maternal blood?
HbF has a much higher affinity for O2 than HbA.
How do muscles extract O2 from the blood?
BY having a higher O2 afinity than HbA
How long is haemoglobin in contact with the alveoli?
ARound 0.75 seconds
IT only takes 0.25 to become saturated though.
How far can PAO2 drop before haem saturation goes below 90%?
PAO2 can go as low as 60mmHg without losing much arterial oxygen