Pulmonary blood Flow, gas exchange, transport- Transport

Question 1

what does blood transport and why?

Answer 1

oxygen from the lungs to the tissues to produce energy to power our cells. - it produces co2 as waste product which is again carried by blood back to the lungs to get rid of in expiration

Question 2

how much oxygen can we dissolve per litre of plasma?

Answer 2

3ml / litre of plasma

• oxygen is not very soluble in water
• not enough to meet energy demnd
• consider red blood cells, (not just plasma), which contain Haemoglobin. This increases the oxygen carrying capacity of whole blood to 200ml
• 200ml of oxygen in whole blood (plasma+red blood cells)

Question 3

what does haemoglobin do?

Question 4

How is most of our co2 diluted?

Answer 4

in various forms, in solution

Question 5

what transport of gas is more compliated

Question 6

what is arterial partial pressure of O2 (PaO2) not the same as?

Answer 6

arterial oxygen concentration content

Question 7

what does PaO2 refer to? what does PaO2 determined by?

Answer 7

O2 in solution in the plasma and is determined by the O2 SOLUBILITY and the PARTIAL PRESSURE OF O2 in the gaseous phase (alveoli) which is driving o2 into solution

Question 8

arterial partial pressure of oxygen (PaO2) is ___ the same as _______

Answer 8

not, arterial oxygen concentration/content

Question 9

what does arterial o2 concentration/content refer to?

Answer 9

• oxygen that is in solution in the plasma
• oxygen that is attached to haemoglobin in the red blood cells

Question 10

calculate the arterial partial pressure of oxygen

Answer 10

o2 solubility = 0.03ml

3ml o2/L plasma so the partial pressure of oxygen that is driving it into solution form gaseous phase (partial pressure at the alveoli) is 3/0.3=100

=> 100mmHg PaO2

Question 11

what is the partial pressure in gaseous phase that is driving that gas into solution equal to?

Question 12

what do gases not travel in in plasma?

Question 13

with no red blood cells, what is the arterial O2 content?

Question 14

what is cardiac output?

Question 15

wht is the o2 demand of resting tissues?

Answer 15

250ml/min

Question 16

describe the effect haemoglobin has on oxygen transport

Answer 16

-

Question 17

what is our total oxygen carrying capacity?

Answer 17

200 ml

Question 18

how saturated is the haemoglobin with oxygen? what is haemoglobin?

Answer 18

98%

• 92% is HbA
• protein, 4 polypeptide chains (2 alpha, 2 beta), each assocaited with an iron containing haem group
• it is the iron heme group which associates with 1 molecule of oxygen
• each haemoglobin molecule carries 4 oxygen molecules

Question 19

What determines how saturated haemoglobin is with oxygen?

Answer 19

The partial pressure of oxygen in arterial blood

Question 20

explain the haemoglobin-oxygen graph

Answer 20

• at normal systemic arterial PaO2 100mmHg, haemoglobin is almost 100% satruated with oxygen
• even as systemi arterial PaO2 decreases to 60mmHg, haemoglobin is still 90% satruated with oxygen

alveolar pressure is moderated decreased- still allows a relatively normal uptake of oxygen to haemoglobin

• partial pressure of oxygen can drop by 40%, yet we only lose 8% satrution of o2 with Hb

=> big safety net, we can have a big fall in partial pressure of oxygen with only a minimum impact of total arterial oxygen content.

• affinity for Hb for oxygen starts to fall rapidly below 60mmHg. Small changes in partial pressure of oxygen start to have bigger changes on the saturation of haemoglboin ith oxygen therefore big efffects on total arterial content.

Question 21

what is the reserve capacity at normal venous PO2?

Answer 21

• partial pressure of resting cell- 40mmHg, haemoglobin is still 75% with oxygen
• 75% reserve capacity
• oxygen delivery to all of our tissues is 1000ml o2/ per min
• we only use/extract 250ml of o2/ 25% that is wrapped up in hb

Question 22

what are the two other types of haemoglobin?

Answer 22

• myoglobin= higher affinity for o2 than haemoglobin
• HbF(foetal)- find in foetus= higher affinity for o2 than haemoglobin
• they get their o2 from the blood, need to have a higher affinity than adult hB TO BE ABLE TO EXTRCT IT FROM THEM and get it into the muscle cell/foetus

Question 23

what does myoglobin and foetal hamogolbin have in relation to normal haemoglobin?

Answer 23

for any given partial pressure, foetal haemoglobin and myoglobin will have a higher affnity for oxygen than adult haemoglobin.

Question 24

what is anaemia?

Answer 24

term where oxygen carrying capacity is compromised

Question 25

how can anemia occur?

Answer 25

• reduced iron deficiency( iron haem groups in haemoglobin which is binding to oxygen)
• haemorrhage- losing red blood cells
• vitamin b12 defiency - needed to make red blood cells

Question 26

whats happens to PaO2 in anaemia?

Answer 26

• stays the same. PaO2 partial pressure of oxygen in arterial blood reflects the amount of oxygen in solution in plasma.

determined by gas solubility nd the partial pressure of oxygen in the gaseous phase(alveoli) driving the gas into solution

• nothing about red blood cells

lost lots of red blood cells- no effect on how much oxygen is moving from alveoli into the plasma

• anaemia , PaO2 normal despite smaller total oxygen content is reduced oxygen carrying capacity in the blood
• anaemia still carries the oxygen fine, just smaller arterial o2 content

Question 27

what happens to PaO2 in anaemia?

Answer 27

PaO2 is normal despite smaller total blood o2 content.

we can have normal PaO2/ partial pressure of arterial oxygen while total blood oxygen content is low

but we cant have low PaO2/partial pressure of arterial oxygen and normal blood oxygen content. it is the partial pressure of oxygen that is determining how much Hb bind to oxygen in red blood cells

Question 28

Answer 28

a) around 100%

=> the PaO2/partial pressure of oxygen in plasma is normal

=> MAIN determinant of haemoglobin saturation is PaO2/partial pressure of oxygen in plasma

=> so haemoglobin saturation is normal

• only issue is NOT A LOT of Hb but it is fully saturated because the PaO2 is normal