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20 Blood gas transport Flashcards

1
Q

What factors determine diffusion on gas exchange?

A
  • Diffusion distance
  • Surface area
  • Moistness
  • solubility of gases
  • Coordination of bloodflow and airflow
  • Concentration gradient (partial pressure)
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2
Q

What is atmospheric pressure at sea level?

A

760 mmHg

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3
Q

Percentage of gases at sea level:

A

N2 78.6
O2 20.9
CO2 0.04
H2O 0.46

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4
Q

Percentage of gases in alveoli:

A

N2 75.4
O2 13.2
CO2 5.2
H2O 6.2

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5
Q

What is alveolar partial pressure

A

Around 758mmHg

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6
Q

What is daltons law?

A

The total pressure exerted by a mixture of gases is the sum of the pressures exerted by each gas in the mixture

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7
Q

What is partial pressure?

A

The pressure exerted by each gas in a mixture. It is directly proportional to the percentage of each gas in the mixture.

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8
Q

How do you work out partial pressure?

A

%gas x pressure

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9
Q

What is the partial pressure of O2 and CO2 in the alveoli vs the arteriole end of capillaries?

A

AC: O2 - 40, CO2 - 45
Alveoli: O2 - 100 CO2 - 40
Once blood reaches the venous end of the capillaries the ppO2 and ppCO2 are the same as in the lungs

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10
Q

What is Henrys law?

A

the amount of gas dissolved that dissolves in water is proportional to the gases partial pressure in air and its solubility

  • at equilibrium the amount of gas dissolved in that substance is proportional to its pp
  • higher pp means more dissolved gas
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11
Q

How soluble are O2 and CO2

A

O2 - not very

CO2 -quite

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12
Q

At ppO2 ____, __ of plasma will dissolve __ O2

A

100
IL
3ml

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13
Q

How much blood flow to the tissues per minute do we have?

A

5L

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14
Q

how much O2 do our tissues need?

A

AT LEAST 200ml/min

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15
Q

How much O2 does 1L of blood contain?

A

195ml

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16
Q

How is our blood able to take more oxygen than it should around the body?

A

using haemoglobin

we don’t dissolve nearly enough in our plasma

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17
Q

What happens to haemoglobin as it takes on oxygen molecules?

A

It changes shape and has a higher affinity for oxygen (take on more oxygen molecules more easily)

18
Q

How many molecules of oxygen can each molecule of haemoglobin carry?

19
Q

How much oxygen is transported by haemoglobin vs plasma?

A

97% H

3% P

20
Q

What is haemoglobin saturation?

A

The percentage of haem units in Hb molecule that contain bound O2

21
Q

What effects O2 binding to Hb?

A
  • Temp (excercise/illness)
  • ppO2
  • pH
  • state of O2 binding in the Hb molecule
22
Q

Which way does the bohr shift move?

A

Right means easier unloading

23
Q

What makes the bohr curve shift to the right?

A 
CADET 
Co2
Acid
Dpg
Exercise
Temperature
24
Q

What is 2,3 DPG?

A

Released in RBCs during glycolysis (their only form of resp due to lack of nutrients). More DPG = more O2 unloading. Is responsible for the limited shelf life of blood in transfusions as more and more DPG is released and effects unloading.

25
Q

What are the other types of haemoglobin?

A

Carboxyhaemoglobin

Methaemoglobin

26
Q

What happens in CO poisoning?

A

CO binds tighter than O2 - competitively
binds permanently
reduces O2 carrying capacity of blood

27
Q

How does methamoglobin come about?

A

Fe2+ is oxidised to Fe3+ by las drogas
Unable to carry O2
can slowly be converted back

28
Q

Fetal haemoglobin

A

Has a higher affinity for O2 (shift to the left)

29
Q

What are the different ways in which CO2 is transported?

A
  • dissolved in plasma
  • As carbonic acid
  • Bound to hameoglobin
30
Q

What % of CO2 is transported in plasma?

31
Q

What % of CO2 is transported as carbonic acid?

A

70% - transported in the blood as HCO3-

32
Q

What % of CO2 is transported bound to haemoglobin?

33
Q

What happens once CO2 enters the blood?

A

93% moves into RBC. 7% dissolves in plasma.
23% then combines with hameoglobin (to a different binding site than oxygen) forming carbaminohaemoglobin.
70% combines with water to form H2CO3 –> HCO3- and H+
HCO3- ions move out into the plasma and Cl- ions move in to keep the cell electrically neutral

34
Q

What transporter do HCO3- ions move out of RBCs via?

35
Q

What is the chloride shift?

A

Cl- ions moving into RBCs to maintain electric neutrality

36
Q

How do RBCs buffer?

A

Haemoglobin and H+ ions released from H2CO3 molecules

37
Q

What are the best buffers in RBCs?

A

Imizadole groups of histidine residues in haemoglobin

38
Q

Which type of hamoglobin has the best affinity for H+?

A

Deoxygenated

39
Q

Describe the process of unloading of CO2 in the lungs:

A
  • Oxygenation of Hb
  • Conformational changes of Hb
  • Lower affinity for H+
  • Decreased buffering power
  • Release of H+
  • Aids unloading of CO2
40
Q

Describe the process of CO2 uptake in the tissues:

A
  • Deoxygenation of Hb
  • Conformational changes
  • Higher affinity for H+
  • Increased buffering power
  • Increased H+ uptake
  • CO2 taken away from tissues

Body Systems (21 decks)

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