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ESA 3 - Respiratory System > Blood Gas Carriage > Flashcards

Flashcards in Blood Gas Carriage Deck (47):
1

Is oxygen soluble in water? 

Not very 

2

How much dissolved oxygen does plasma contain at a partial pressure of 13.3kPa and a temperature of 37oC?

0.13mmol/L

3

How much oxygen do we need at rest? 

12mmol per minute 

4

What volume of plasma would be required to meet the bodys oxygen requirements if the only source was dissolved oxygen? 

92L

5

What is the typical ppO2 in the lungs? 

13.3kPa

6

What is the typical ppO2 in the tissues? 

~5kPa

7

Draw an oxygen haemoglobin dissociation curve

A image thumb
8

What does haemoglobin do? 

With respect to oxygen binding

Reversibly binds to oxygen over a very narrow range of ppO2

9

Describe the structure of haemoglobin 

Tetrameric protein, made up of 2 α and 2 ß subunits, with 4 haem groups 

10

What is the result of haemoglobin having 4 Haem groups? 

It can bind to four molecules of oxygen 

11

What factors can decrease the affinity of Hb for O2?

  • H+
  • Increasing temperature 
  • Increased CO2

 

12

What happens at sites of low pH and increased CO2?

More oxygen is required and will be released 

13

What tissue may experience low pH and increased CO2?

Muscle tissue during exercise 

14

What is the effect of low pH and increased CO2 on haemoglobin dissociation called? 

The Bohr effect

15

What happens to the oxygen dissociation curve as a result of the Bohr effect? 

It shifts to the right 

16

Draw a graph illustrating the effect of changing conditions on the oxygen dissociation curve

A image thumb
17

What happens if the pO2 in the capillaries falls? 

pH falls and temperature falls, so Hb will give up more oxygen

18

What is the result of a pO2 fall in the capillaries on the saturation of Hb leaving the capillaries? 

It is greatly reduced 

19

What can be used to calculated the percentage of oxygen that has been given up in a tissue if venous pO2 is known? 

A dissociation curve 

20

What happens to blood flowing through alveolar capillaries? 

It picks up oxygen and looses carbon dioxide by diffusion of those gases across the alveolar wall 

21

What is the rate at which gases exchange determined by? 

  • Area available for exchange
  • Resistance to diffusion 
  • Gradient of partial pressure 

 

22

What can be used to calculate the transfer factor of the lungs? 

Carbon Monoxide 

23

What reactions can carbon dioxide undertake in the blood? 

  • Dissolves in water
  • Reacts in water 
  • Binds directly to proteins 

 

24

How does the solubility of carbon dioxide compare to that of oxygen? 

It is more soluble 

 

25

What does carbon dioxide form when it reacts with water? 

Hand HCO3-

26

Is the reaction of carbon dioxide and water reversible? 

Yes, depending on the concentration of reactants 

27

What is formed when carbon dioxide binds directly to proteins in the blood? 

Carbamino compounds 

28

What is the Henderson-Hasselbach equation? 

pH = 6.1 + Log( [HCO3-] / (pCO2 x 0.23) ) 

29

What happens to carbon dioxide in plasma?

It dissolves in plasma and undergoes a slow reaction with water, creating HCO3-

30

Why does carbon dioxide undergo a slow reaction with water in plasma? 

Because there is little carbonic anhydrase 

31

What happens to carbon dioxide in RBCs? 

It reacts with water rapidly to form Hand HCO3-

32

Why does carbon dioxide react with water rapidly in RBCs? 

Because carbonic anhydrase is present

33

What happens to the H+ ions formed in carbon dioxides reaction with water in RBCs? 

They bind to Hb

34

What is the result of H+ ions binding to Hb? 

It draws the reaction towards HCO3-

35

What does the amount of HCO3produced by carbon dioxide reacting with water in RBCs depend on? 

Primarily, the buffering effects of Hb

36

Why can Hb be said to act as a buffer? 

H+ ions bind to Hb, so it acts as a buffer by 'mopping up' the ions 

37

What does the buffering action of Hb drive? 

The reaction of carbon dioxide and water, and therefore the production of Hand HCO3-

38

What do carbamino compounds do? 

Bind directly to proteins

39

What does the binding of carbamino compounds to proteins contribute to? 

Carbon dioxide transport 

NOT acid base balance 

40

Are more carbamino compounds formed in arterial or venous blood? 

Slightly more in venous blood 

41

Why are there slightly more carbamino compounds formed in venous blood? 

Because pCO2 is higher 

42

What is the normal carbon dioxide content of arterial blood? 

21.5 mmol/L

43

What is the normal carbon dioxide content of venous blood? 

23.5 mmol/L

44

How much carbon dioxide is transported from the tissues to the lungs? 

2mmol/L

45

How is the amount of carbon dioxide transported from the tissues to the lungs calculated? 

Venous blood carbon dioxide - Arterial blood carbon dioxide

46

In what forms does carbon dioxide travel from the tissues to the lungs? 

  • 80% travels as HCO3-
  • 11% travels as carbamino compounds
  • 8% travels as dissolved CO2

 

47

What does the amount of CO2 that travels from the tissues to the lungs as HCO3- depend on? 

How much O2 has been lost, allowing it to bind to H+