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Physiology 2 Flashcards

1
Q

What are the 2 main circulations that supply blood to the lungs?

A

bronchial and pulmonary circulation
Bronchial- bronchial arteries supply the airway smooth muscle, nerves and lung tissue
Pulmonary- the left and right pulmonary arteries each supply one lung and surround the alveoli with blood vessels; thus allowing transport of deoxygenated blood to the lungs and oxygenated away from lungs

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2
Q

what kind of system is the pulmonary system?

A

low pressure, high flow system

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3
Q

What is the CO of the RV and how does this flow rate compare to that of the rest of the body?

A

5L/min, which is the same as the left side of the heart

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4
Q

What is a difference between the pulmonary and systemic circulation?

A
  • pulmonary circulation is much lower pressure than systemic (approx 25mmHg in pulmonary & 120mmHg in systemic)
  • much lower difference in pressure between arterial and venous sides in pulmonary circulation than systemic
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5
Q

what is the difference between pulmonary artery and pulmonary vein and why is this significant?

A

only about 10mmHg, significant because since this is such a small pressure difference, it doesn’t take very much pathology to disrupt it, lose gradient and impede blood flow through lungs

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6
Q

what causes oxygen to go form inside alveoli to pulmonary vein and co2 to go from inside pulmonary artery to alveoli?

A

partial pressure gradient (high to low)

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7
Q

what is PA02?

A

alveolar partial pressure of o2 (100mmHg)

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8
Q

What is PACO2?

A

alveolar partial pressure of co2 (40mmHg)

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9
Q

Pa02?

A

arterial partial pressure of 02 (100mmHg)

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10
Q

PaCO2?

A

arterial partial pressure of co2 (40mmHg)

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11
Q

Pv02?

A

venous partial pressure of 02 (40mmHg)

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12
Q

PvCO2?

A

venous partial pressure of CO2 (46mmHg)

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13
Q

what do you do to calculate kPA from mmHg?

A

multiply by 0.133

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14
Q

what factors affect the rate of diffusion across a membrane? (5)

A
  • directly proportional to partial pressure gradient
  • directly proportional to gas solubility
  • inversely proportional to membrane thickness
  • directly proportional to available surface area
  • fastest over short distances
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15
Q

what is a way in which the lungs are set up to allow maximal diffusion?

A

nothing in between type 1 alveolar cells and blood vessels (aka elastic fibres etc)

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16
Q

what are characteristics of emphysema?

A

reduction in lung elasticity, degradation of alveolar wall, reduced surface area for gas exchange, decreased Pa02

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17
Q

what are characteristics of fibrotic lung disease and how it affects gas exchange?

A

fibrous tissues sit in between type 1 alveolar cells & capillaries and inhibit diffusion, and also reduce lung expansion- reduced PA02

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18
Q

what are the characteristics of pulmonary oedema and how it affects gas exchange?

A

fluid building up between alveolus and capillary - increases diffusion distance and therefore impedes movement of oxygen

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19
Q

what are the characteristics of asthma and how it affects gas exchange?

A

increased resistance to air flow, reduced ventilation, reduced PA02

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20
Q

what is ventilation and how is it measured?

A

air flow to alveoli, measured in L/min

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21
Q

what is perfusion and how is it measured?

A

local blood flow, L/min

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22
Q

why are ventilation and perfusion not ideally matched?

A

because of gravity

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23
Q

where is perfusion greatest?

A

at base of lung

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24
Q

where is ventilation greatest?

A

at base of lung

25
what pressure is greatest at the base of the lung?
perfusion- more blood at base of lung (gravity), arterial pressure exceeds alveolar pressure & compresses alveoli, vascular resistance is low
26
what pressure is greatest at the apex of the lung?
ventilation- alveolar pressure greater than BP, blood vessels get compressed, vascular resistance increased
27
where is the middle point in the lungs where ventilation= perfusion?
rib 3
28
where is ventilation/perfusion ratio > 1?
the apex
29
where is ventilation / perfusion ratio <1?
base of the lung
30
what happens when ventilation < perfusion ?
buildup of co2 in alveoli, so increase in PAco2 and decrease of Pa02 in capillaries. Increase in PAc02 will result in a loss in the partial pressure gradient between pulmonary artery and alveoli - this means blood going back to the heart is still almost completely deoxygenated; effectively being 'shunted' from right side to left side of heart
31
what auto regulation mechanisms can happen to try keep ventilation and perfusion balanced in ventilation < perfusion scenario?
- vasoconstriction as a result of hypoxia - divert blood to better ventilated regions - co2 increase causes mild bronchodilation
32
what are the effects of auto regulation in a situation of ventilation < blood flow?
decreased perfusion | increased ventilation
33
what happens when ventilation > perfusion?
alveolar dead space - increase in Pa02 - reduced PAC02
34
what are the effects of auto regulation in a situation of ventilation > perfusion?
- increase in Pa02 --> pulmonary vasodilation | - reduced PAC02--> bronchial constriction
35
what is alveolar dead space ?
alveoli that are ventilated but not perfused
36
what is anatomical dead space ?
air that cannot take part in gas exchange because the walls of the conducting airways are too thick
37
what is physiological dead space?
alveolar + anatomical
38
how much oxygen dissolves per litre of plasma?
3ml/L
39
what does arterial partial pressure of oxygen refer to?
the amount of oxygen dissolved in plasma
40
why do gases not travel in gaseous phase in plasma?
this would result in bubbles of air in blood which would result in a fatal air embolism
41
how much oxygen does Hb carry and how saturated is it?
carries 197ml/L, roughly 97-98% saturated because some Hb molecules only bind 3 molecules of oxygen
42
how does haemoglobin work?
it has a very high affinity for oxygen and pulls oxygen out of plasma. Until it is fully saturated it will therefore continue to draw oxygen out of alveoli
43
what is haemoglobin made up of?
- 2 alpha and 2 beta chains - one molecule can bind 4 molecules of oxygen. When one molecule binds this increases the affinity of haemoglobin to oxygen and therefore more binds - when oxygen leaves, the binding sites shut down and reduces affinity (co-operative binding)
44
What is the majority form of Hb in RBCs?
around 92% is in the form HbA
45
Why is glycosylated haemoglobin important clinically?
gives indication of exposure to glucose
46
what is the major determinant of the degree to which haemoglobin is saturated with oxygen?
partial pressure of oxygen in arterial blood (how much oxygen has dissolved in plasma)
47
what 2 other types of haemoglobin are there and compare their affinities compared to normal adult haemoglobin
Myoglobin and Fetal Haemoglobin - much higher affinity to 02 than normal adult haemoglobin
48
what is anaemia?
where the oxygen carrying capacity of the blood is compromised, mostly due to reduction of number of RBCs (iron deficiency, lack of vitamin B12)
49
what remains normal in anaemia?
the partial pressure of oxygen in arterial blood
50
what alters in anaemia (to do with no of RBCs)
reduced number of RBCs so total oxygen content falls, however % saturation remains the same
51
affinity of Hb for oxygen remains high until the p02 falls below ..?
60mmHg
52
what 4 factors affect the affinity of haemoglobin for oxygen by decreasing the affinity?
- decrease pH - binding 2,3-DPG - increase in temperature - increase in pCO2
53
how does CO lead to pathology?
CO binds to Haemoglobin to form CARBOXYHAEMOGLOBIN, and has a much higher affinity for Hb than oxygen does. It becomes very stable once it is bound to it and therefore does not easily dissociate from it which is problematic
54
does CO affect respiratory rate?
no, because the PaCO2 is unaffected
55
what are symptoms of CO poisoning?
- anaemia - hypoxia - cherry red skin - mucous membranes - nausea and headaches
56
what are the 5 types of hypoxia and describe them (mnemonic)
(HIHAM) Hypoxic - reduction in diffusion a lungs due to decrease in Patm02 / pathology Ischaemic- the heart does not receive enough oxygen and therefore cannot pump enough to lungs/around body Histotoxic- poisoning prevents cells utilising oxygen e.g. CO Anaemic - reduction in oxygen carrying capacity of blood due to anaemia Metabolic- when blood pumped to a tissue is not enough to meet the increased energy demand by cells
57
how is Co2 transported in the blood? (3 ways)
- 7% dissolves in plasma & RBCs - 23% binds to deoxyhaemoglobin to form carbamino compounds in RBCs - 70% binds to water to from CARBONIC ACID which then dissociates to form bicarbonate ions and hydrogen
58
how is co2 capable of changing blood pH?
CO2 + H20 H2CO3 HCO3 + H+ Normally pH stable because all CO2 produced is able to be expired through expiration however; in hyperventilation, more co2 blown off than is being produced, decreased H+, respiratory alkalosis in hypoventilation, co2 retention, H+ increases, respiratory acidosis

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