Lungs Flashcards
(126 cards)
1
Q
How many zones can the trachea > alveoli be divided into?
A
24 (0-23)
2
Q
Which are the conducting zones?
A
First 17
3
Q
Which zones are highly cartilaginous and have their own blood supply?
A
First 4
4
Q
Which are the respiratory zones?
A
Last 6
5
Q
Why do particulates settle before the alveoli?
A
Velocity falls as flow is distributed
6
Q
What is the expiratory/inspiratory reserve volume?
A
Everything you can breathe out/in after normal breathing
7
Q
Which values can’t be measured by spirometry?
A
Residual volume and functional residual capacity
8
Q
What is functional residual capacity?
A
Residual volume + expiratory reserve volume
9
Q
What is distending pressure?
A
Positive transpulmonary pressure to keep lungs inflated
10
Q
Volume of one mole of dry ideal gas?
A
22.4 litres
11
Q
How is the conducting zone kept open?
A
Kept open by elastic connections between airways and lung parenchyma
12
Q
What is the most important variable determining alveolar ventilation?
A
Frequency
13
Q
Why is water vapour not an ideal gas?
A
pV =/= nRT because n changes with temperature
14
Q
WHat is anatomic dead space?
A
Conducting portion
15
Q
What is alveolar dead space?
A
Little or no blood flow
16
Q
What is expired minute volume?
A
Air in and out of lungs per unit time
17
Q
Why is expired minute volume not quite right?
A
V in =/= V out because more O2 in than CO2 out
18
Q
What % of expired CO2 has come from alveoli?
A
All of it
19
Q
What happens to alveolar PCO2 as alveolar ventilation increases?
A
Decreases
20
Q
Why does alveolar PN2 increase?
A
Because RER
21
Q
Why is total pressure in venous blood below atmospheric?
A
Because PO2 decreases more than PCO2 increases
22
Q
What happens to arterial PCO2 if you double VA?
A
Halves
23
Q
What will rectify a doubling of PACO2?
A
Doubling ventilation
24
Q
Why must alveolar PO2 decrease if arterial PCO2 rises?
A
Pressure can’t exceed atmospheric
25
Why must alveolar ventilation increase after exercise?
Alters CO2 production and therefore VECO2
26
WHat is static compliance?
Measured when no air flow
27
What is normalised static compliance called?
Specific
28
What is FRC?
Equal and opposite compliance recoil forces of chest wall and lung
29
What happens to FRC is a less compliant lung?
Lung pulls in more so lower FRC
30
What can causes a less compliant lung?
Elevated diaphragm, muscle rigidity
31
What does DPPC stand for?
Dipalmitoyl phosphadityl choline
32
Which parts of DPPC are in gas and which are in air?
Palmitate in gas, glycerol, choline and phosphate in liquid
33
Three roles of surfactant?
Reduce surface tension, allow different-sized alveoli to coexist, keep alveoli dry
34
How does surfactant allow different-sized alveoli to coexist?
Pressure = 2T/r so smaller alveoli have more pressure so gas would flow small>big. Surfactant lowers T in small alveoli.
35
How does surfactant keep alveoli dry?
Force collapsing alveoli would also pull water from capillaries, surfactant reduces ability to do this
36
What is the flow in between laminar and turbulent called?
Transitional
37
When do you get peak flow rate? Why?
Large lung volume because elastic recoil pressure highest
38
Where is airway resistance highest?
Very high because there are lots of branches in parallel at lower areas
39
Where is equal pressure point at high and low lung volume?
Further down at low lung volume (less elastic recoil), low compliance tissues at high lung volumes
40
Factors affecting airway resistance?
Lung volume, bronchial smooth muscle, gas viscosity and density
41
What happens to forced expiratory flow in obstructive diseases?
Lower - same lung capacity but can't expire at high rate
42
What happens to forced expiratory flow in restrictive diseases?
The same - same expiration rate but lower lung capacity
43
Why can PO2 sometimes not be reached fast enough if diffusion reserve increases?
CO2 solubility is greater so it diffuses faster
44
Which chains does haemoglobin have?
2 alpha, 2 beta
45
Which chain is wrong in HbS?
AA substitution in beta chain
46
Whihc type of Hb is less sensitive to DPG?
HbF
47
What does DPG do to curve?
Keeps it right-shifted
48
What shifts Hb saturation curve to the right?
Decreased pH, increased PCO2, increased DPG
49
What is PO2 of maternal blood to fetus? Why is this significant?
30 - large Hb saturation difference here
50
What is hypercapnia?
Excess CO2 from hypoventilation
51
What is hypocapnia?
Below normal PCO2 from hyperventilation
52
What is hypoxic hypoxia?
Low arterial PO2 and inadequate Hb
53
What is anaemic hypoxia?
Reduced ability to carry O2, low RBC count
54
What is circulatory hypoxia?
Too little blood
55
What is histotoxic hypoxia?
Normal O2 delivery but can't use it eg) cyanide
56
What happens in capillary blood takes too long to reach equilibrium?
Out of breath
57
WHy is Hb not affected by barometric pressure variations?
Virtually saturated above 60mmHg
58
Three ways to transport CO2?
Dissolved, carbamino compunds, bicarbonate
59
How does CO2 bind to protein?
Reversibly binds to amine group
60
How does the Haldane effect graph work?
Plot a line for PO2 = 40 (veins) and then see how much CO2 is lost between different PCO2s BUT PO2 also changes so must compare between different curves
61
What must happen if one HCO3- is moved?
Must be replaced with Cl- to prevent electrochemical gradient forming
62
What ratio must stay the same for pH to stay at 7.4?
[CO2] : [HCO3-]
63
What should be the pKa of a good buffer?
7.4, so kidney can release or withold HCO3- into urine
64
What do Davenport diagrams show?
Relationship between pH, pCO2 and HCO3-
65
What happens to pulmonary resistance as arterial pressure increases? Why?
Decreases - more pulmonary vessels are recruited and then they distend
66
What are the two circulatory systems in the lungs?
Bronchial (to serve conducting airways) and pulmonary for gas exchange
67
How does pulmonary circulation protect organs against emboli?
Endothelial cells release fibrinolytic enzymes and absorb air emboli
68
Why is pulmonary circulation a passive system?
Autonomic nerves don't control diameter
69
What happens to blood vessel diameter at high lung volumes?
Reduced because alveoli stretch vessels, the others increase their diameter because of -ve pleural pressure
70
Where is pulmonary vascular resistance lowest?
Very close to FRC (optimum balance)
71
What is regional hypoxia?
Reduced blood to hypoxic areas, localised vasoconstriction and compensatory dialtion somewhere else
72
What is general hypoxia?
Reduced blood flow to all areas, eg) CF or oedema from high blood pressure
73
What can cause pulmonary oedema?
Left heart failure causing increased capillary pressure, oxidant damage and endotoxins cause increase in capillary permeability, loss of plasma proteins decreases colloid osmotic pressure, lymphatic blockage
74
How does lack of surfactant increase intersitial pressure?
Increases surface tension
75
Why does drowning in fresh water cause cardiac arrest?
RBCs burst, K+ released from inside and Na+ is diluted
76
What is usual value of Va/Q ratio?
0.8
77
What are units of Va/Q ratio?
No units
78
Which area of the lungs is Va/Q ratio lower in?
The bottom
79
Does ventilation or perfusion have a larger difference top to bottom?
Perfusion
80
How do high Va/Q ratios affect blood O2 content?
Minimal effect because ventilation wasted, PCO2 falls so pH increases so localised increases in airway resistance so ventilation shifted to other alveoli.
81
How do low Va/Q ratios afect blood O2 content?
Large effect - Increase in overall ventilation to compensate, acute response, regional vasoconstriction from localised hypoxia shunts blood from poorly ventilated alveoli
82
Two causes of venous admixtures?
Shunting or low Va/Q ratio
83
What are the types of shunting?
R>L anatomic or alveolar (passes alveolus but doesn't contact air from pneumonia/collapsed alveoli)
84
What does the apneustic centre do?
Prolongs inspiration
85
What does the pneumotaxic centre do?
Inhibits inspiration
86
What does vagal afferent input do?
Terminates inspirations
87
What does cutting below medulla do?
Stops breathing
88
What does cutting above central medulla do?
Rhythmic but irregular breathing
89
What does cutting at upper pons do?
Slows respiration but increases tidal volume
90
What happens if saline and CO2 is added to chemosensitive areas?
Add CO2 and ventilation increases, add saline and it decreases
91
What produces cerebrospinal fluid?
Choroid plexus
92
What is the composition of cerebrospinal fluid?
Low protein, HCO3-, K+ and Ca2+. High Na+, Cl-
93
Are carotid or aortic bodies dominant in breathing control?
Carotid
94
Which cells in the carotid bodies are responsible?
Glomus
95
What can carotid bodies sense?
PCO2, pH, PO2
96
What do the pulmonary stretch receptors in the airway do?
Discharge in response to distension via the vagus nerve
97
What is the Hering-Breuer inflation reflex?
Discharge of pulmonary stretch receptors slows breathing frequency by inhibiting inspiration and prolonging expiration
98
What is the deflation reflex?
Lung deflation induces inspiration
99
What must tidal volume be greater than for CPG?
1 litre
100
What happens to tidal volume and breathing frequency if vagal afferent input to higher brain is blocked?
Nothing
101
What does the intrinsic ramp pattern of the pontine respiratory group do?
Stimulation terminates inspiration, still get breathing pattern if afferent input is cut
102
What does the apneustic centre innervate?
Respiratory muscles
103
Why is blood flow bad at the top of the lung?
Alveolar pressure is greater than artery and vein pressure, so blood vessels closed
104
Why is blood flow good a the bottom of the lung?
Artery and vein pressure greater than alveolar pressure so vessels stay open
105
What are the ventilation/perfusion zones of the lung called?
West Zones
106
Are the base and apex over-perfused or over-ventilated?
Base is overperfused, apex is over-ventilated
107
How do the medullary central chemoreceptors monitor PCO2?
Use H+ (CO2 crosses blood-brain barrier into CSF and forms H+)
108
Why can't protons in blood just cross the blood brain barrier to the chemoreceptors?
They could have come from lots of places
109
What does cutting pneumotaxic centre cause?
Goes to full tidal volume because pneumotaxic centre aids inspiration termination
110
What does cutting apneustic centre do?
Get small variable inhalations because it contains motor nerves which drive inspiration
111
What do stretch receptors carried by the vagus stimulate?
Pneumotaxic which inhibits apneustic so exhalation
112
What is rate limiting at altitude?
O2 diffusion
113
What do hyperventilation at altitude do?
Decreases PCO2 so alveolar PO2 increases again - BUT falling PCO2 opposes low PO2 which triggers ventilation increase
114
Hyperventilation at altitude causes alkaline CSF - what does this do?
Choroid plexus stops producing HCO3- which removes the "braking effect" - a good thing here.
115
What is Caisson disease?
The bends
116
Why is He used instead of N2?
Reduces bends risk because it's half as soluble
117
What is the neurogenic response?
Increases Ve at the start of exercise
118
What does the humeral response do?
Maintains increased Ve during exercise
119
Why don't PCO2, PO2 and pH not change during exercise?
NOBODY KNOWS
120
What do peripheral chemoreceptors control?
Adding/removing CO2
121
What can blood supply vasoconstriction during low O2 cause?
High pressure so fluid pools in alveoli
122
What is the vicious circle from chemoreceptors signalling opposite things at altitude?
Normal CO2 and decreased O2 > increased ventilation > increased O2 and decreased CO2 > decreased ventilation > back to where we started
123
What is "central adaptation"?
To stop decreased ventilation, [HCO3-] is removed from CSF so more H+ produced (so goes back to normal) which is detected by chemoreceptors so ventilation increases again - NOT TO MAKE VENTILATION INCREASE, JUST TO STOP IT GOING DOWN
124
What is the Haldane effect?
The CO2 content of blood is modulated by PO2/saturation - more CO2 is carried in deoxygenated that oxygenated blood
125
Why is more CO2 carried in deoxygenated than oxygenated blood?
Deoxy Hb is a weaker acid so will bind more protons at physiological pH which maintains gradient for bicarb production AND deoxy Hb forms more carbamino compounds
126
Why is the slope of "adding carbonic acid" line steeper on a Davenport diagram than titrating plasma?
Because of Hb buffering properties
