Respiratory physiology Flashcards
1
Q
What are the functions of the respiratory system?
A
Gas exchange
Acid base balance
Protection from infection
Communication via speech
2
Q
Why is gas exchange so important?
A
Oxygen is supplied to tissues and CO2 is removed
3
Q
What is external respiration?
A
Movement of gases between the air and the body’s cells
4
Q
What do the pulmonary artery and vein carry?
A
Artery- Deoxygenated blood away from the heart
Vein- oxygenated blood towards the heart
5
Q
Where is the division of the upper and lower respiratory tracts?
A
Larynx
6
Q
What is the epiglottis and its function?
A
Small flap of tissue that folds over the trachea to prevent food or liquid from entering the airway
7
Q
At what vertebral level does the trachea bifurcate?
A
T4
8
Q
What are the lobes of the right lung?
A
Superior
Middle
Inferior
9
Q
What are the lobes of the left lung?
A
Superior and inferior
10
Q
What lobes does the horizontal tissue split?
A
Superior and middle
11
Q
What lobes does the oblique tissue split?
A
Inferior and superior/middle
12
Q
What does the trachea branch into?
A
Bronchi
13
Q
What is the carina?
A
Bifurcation of the trachea?
14
Q
Why do the bronchi and trachea have cartilaginous rings?
A
Maintain patency of the airway
15
Q
What do the bronchi branch into?
A
Bronchioles
16
Q
What maintains the patency of the bronchioles?
A
Physical forces from the thorax
17
Q
Where is the most resistance to airflow present?
A
Trachea and bronchi
18
Q
What 3 types of cell are resent in the alveoli?
A
Type 1 pneumocytes, type 2 pneumocytes, macrophages
19
Q
What is the function of type 1 and 2 pneumocytes?
A
1- thin cells that allow for gas exchange
2- produce surfactant
20
Q
What is the function of surfactant?
A
Reduce surface tension and prevent small alveoli from collapsing
21
Q
Describe the use of the elastic fibres in the alveoli walls?
A
Stretched during inspiration
Energy invested during inspiration is then released allowing for passive expiration
22
Q
What kind of epithelium lines the respiratory tract?
A
Pseudostratfied ciliated columnar epithelium
23
Q
What are the differences in the epithelium travelling down the respiratory tract?
A
Cells become more squamous
Goblet cells then cilia lost
24
Q
What is the function of mucus in the respiratory tract?
A
Moisten air
Traps particles
25
What is Boyle's law?
Pressure exerted by a gas is inversely proportional to its volume
26
What is Dalton's law?
Total pressure of a gas mixture is the sum of the pressures of the individual gases
27
What is Charles' law?
Volume occupied by a gas is directly related to the absolute temperature
28
What is Henry's law?
Amount of gas dissolved in a liquid is determined by the pressure of the gas and its solubility in the liquid
29
What is the hilum of the lung?
Site of the root
30
What is the root of the lung?
Entry and exit of major vessels and airways
31
What structures exist at the root of the lung?
Pulmonary arteries and veins
| Bronchus
32
What are the 2 aspects of the pleural membrane?
Parietal- lines ribs and diaphragm
| Visceral- lines surface of lungs
33
What is the pleural cavity?
The space between the 2 pleural membranes
34
What is the function of the intrapleural fluid?
Allows membranes to glide across each other and prevents membranes from separating
35
What is pleurisy?
Inflammation of the pleural membranes, causing them to grate across each other, causing pain
36
What creates an equilibrium at the end of a breath?
Attachment of the chest wall (that naturally want to expand) to the lungs (that naturally want to recoil) by the pleural membranes
37
What draws the air into the lungs?
The negative pressure in the pleural cavity caused by the equilibrium between the lungs and chest wall
38
What muscles are used for inspiration?
Diaphragm and external intercostals
39
What muscles are used for expiration?
Abdominals and internal intercostals
40
What are the accessory muscles of inspiration?
Scalenes and sternocleidomastoids
41
What is the intra-thoracic pressure?
Pressure inside the thoracic cavity i.e. alveoli
42
What is the intra pleural pressure?
Pressure inside the pleural cavity
43
What is the transpulmonary pressure?
Difference between intra-thoracic and intra-pleural pressure
| This is always positive as Pip is more negative than PA
44
What is the bulk flow of air between the atmosphere and alveoli directly proportional to?
Difference between the alveolar and atmospheric pressures
45
What is the bulk flow of air between the atmosphere and alveoli inversely proportional to?
Airway resistance
46
What happens at the end of a passive expiration?
The atmospheric and alveolar pressures are equal, and the dimensions of the thoracic cage and lungs are stable as a result of opposing elastic fibres creating a subatmohpheric intrapleural pressure
47
What is the major determinant of airway resistance?
Radii of airway
48
What is the anatomical dead space?
The volume of gas occupied by the conducting airways- this gas is not available for exchange
49
What volume of gas is in the anatomical dead space at any one time?
About 150ml
50
How much is tidal volume?
500ml between 2.3 and 2.8 litres
51
What is the residual volume?
Volume of gas left in the lungs at the end of expiration to prevent the alveoli from collapsing and provide a reservoir of air for continuous gas exchange
52
How much is residual volume?
1.2 litres
53
What is inspiratory reserve volume?
Additional air that can be forcibly inhaled after inspiration of the normal tidal volume
54
How much is inspiratory reserve volume?
3 litres
55
What is expiratory reserve volume?
Additional air that can be forcibly exhaled after exhalation of the normal tidal volume
56
How much expiratory reserve volume?
1.2 litres
57
What is the total lung capacity?
Maximum amount of air that fills the lungs
58
How much is total lung capacity?
6 litres
59
What is vital capacity?
The total amount of breath that can be exhaled in 1 breath after fully inhaling
60
How much is vital capacity?
4.8 litres
61
What is inspiratory capacity?
The total amount of air that can be inspired in 1 breath
62
How much is inspiratory capacity?
3.6 litres
63
What is the functional residual capacity?
The amount of air remaining in the lungs after normal expiration
64
How much is functional residual capacity?
2.4 litres
65
What is pulmonary ventilation?
Total air movement into/out of lungs
66
What is alveolar ventilation?
Fresh air getting into the alveoli available for gas exchange
67
What is partial pressure?
The pressure of one particular gas in a mixture of gases
68
How is partial pressure calculated?
Percentage of that particular gas in the mixture multiplied by the pressure of the entire mixture
69
What is atmospheric pressure?
760mmHg, 101kPa
70
Under normal conditions, what are the partial pressures of O2 and CO2?
```
PO2= 100mmHg
PCO2= 35mmHg
```
71
What is surfactant?
Detergent type liquid produced by type 2 pneumocytes
72
What is the function of surfactant?
Reduce surface tension on alveolar surface to prevent alveolar collapse, particularly in smaller alveoli
73
How does surfactant work?
Sits between water molecules on the alveolar surface and reduces attraction between them, therefore reducing the inward pressure that would cause alveoli to collapse
74
How is pressure inside alveoli calculated?
2(surface tension) x radius of sphere
75
When in gestation is surfactant produced?
25-36 weeks
76
What stimulates surfactant production?
Thyroid hormones and cotisol
77
What is compliance?
The change in lung volume relative to the change in pressure
78
What does compliance represent?
The stretchability of the lungs
79
What is high compliance?
Large increase in volume for small increase in pressure- little effort required
80
What is low compliance?
Small increase in volume for a large decrease in intrapleural pressure
81
What does high/low compliance indicate?
High- doesn't necessarily indicate healthy lungs e.g. emphysema
Low- never healthy e.g. fibrosis
82
How can the pressure changes of inspiration and expiration be compared?
It requires a greater change in pressure to reach a particular lung volume in inspiration than maintain it in expiration
83
Where in the lung is compliance greatest?
Base
84
Where in the lung is compliance least?
Apex
85
Why is compliance greater at the base than the apex of the lung?
Alveoli at the base of the lung are 'squashed' more at the end of expiration and therefore have a greater range of inflation
86
What happens in an obstructive lung disease?
Obstruction of airflow, particularly on expiration
87
What happens in a restrictive lung disease?
Restriction of lung expansion
88
What is a normal FEV1/FVC?
80%
89
What is FEV1/FVC in obstructive and restrictive lung diseases?
```
Obstructive= low %
Restrictive= normal-high %
```
90
What is bronchial circulation?
Circulation supplying oxygenated blood to the bronchial smooth muscle, nerves and ling tissue
91
What is pulmonary circulation?
Carries deoxygenated blood to the lungs for oxygenation
92
What is the rate of diffusion across the membrane affected by?
Directly proportional to the partial pressure gradient, gas solubility and available surface area
Inversely proportional to the thickness of the membrane
93
How does emphysema affect gas exchange?
Destruction of alveoli reduces surface area for gas exchange
94
How does fibrotic lung disease affect gas exchange?
Thickened alveolar membrane slows gas exchange
95
How does pulmonary oedema affect gas exchange?
Fluid in interstitial space increases diffusion distance and slows gas exchange
96
What is the distribution of blood flow across the lung?
Declines with height across the lung
97
Why is blood flow high at the base of the lung?
Arterial pressure is higher than alveolar pressure, decreasing vascular resistance
98
Why is blood flow lower at the apex of the lung?
Alveolar pressure is greater than arterial pressure, increasing vascular resistance
99
Where are ventilation and perfusion at their greatest?
At the base of the lung
100
What is the V/Q ratio like at the base of the lung?
Low
101
What is the V/Q ratio like at the apex of the lung?
High
102
What is alveolar dead space?
Alveoli that are ventilated but not perfused
103
What is anatomical dead space?
Air in the conducting zone of the respiratory tract unavailable for gas exchange
104
What is physiological dead space?
Alveolar and anatomical dead space
105
What is used to transport oxygen in the blood?
Haemoglobin
106
How is the bulk of CO2 transported in the blood?
In solution in the plasma
107
What does partial pressure of arterial O2 refer to?
The O2 in solution
108
What is the partial pressure of arterial O2 determined by?
O2 solubility and the partial pressure of O2 in the gaseous phase
109
What is normal PaO2?
100mmHg
110
What is the O2 demand of tissues at rest?
250ml/min
111
How much oxygen binds to 1g of haemoglobin?
1.34ml
112
What is O2 saturation of haemoglobin at 100mmHg?
98%
113
What types of haemoglobin have a higher oxygen affinity?
Foetal Hb and myoglobin
114
What is anaemia?
Any condition where the oxygen carrying capacity of blood is compromised
115
What can cause anaemia?
Iron deficiency
Haemorrhage
Vitamin B12 deficiency
116
What factors affect the oxygen dissociation curve?
pH
PCO2
Temperature
117
What effect does pH have on the oxygen dissociation curve?
Decrease- decreases affinity of Hb for O2
| Increase- Increases affinity of Hb for O2
118
What effect does PCO2 have on the oxygen dissociation curve?
Decrease- increases affinity of Hb for O2
| Increase- decreases affinity of Hb for O2
119
What effect does temperature have on the oxygen dissociation curve?
Decrease- increases affinity of Hb for O2
| Increase- decreases affinity of Hb for O2
120
What effect does CO have on oxygen binding to Hb?
CO has a higher affinity for Hb and prevents O2 from binding
121
What are the symptoms of CO poisoning?
Hypoxia and anaemia
Nausea and headaches
Cherry red skin and mucous membranes
122
What are the 5 main types of hypoxia?
```
Hypoxic
Anaemic
Ischaemic
Histotoxic
Metabolic
```
123
What is hypoxic hypoxia?
Reduction in O2 diffusion at lungs due to decreases atmospheric PO2 or tissue pathology
124
What is anaemic hypoxia?
Reduction of O2 carrying capacity of blood due to anaemia
125
What is ischaemic hypoxia?
Heart disease, resulting in inefficient pumping of blood to the lungs and around the body
126
What is histotoxic hypoxia?
Poisoning prevents cells utilising oxygen delivered to them
127
What is metabolic hypoxia?
Oxygen delivered to tissues does not meet increased oxygen demand by cells
128
By what 3 methods is CO2 transported in the blood?
7% dissolved in plasma
23% combines with deoxyhaemoglobin to form carbamino compunds
70% combines with erythrocytes and water to form carbonic acid, which dissociates to give bicarbonate and H+
129
What is the chloride shift?
Movement of bicarbonate out of the blood stream and Cl- ions into it
130
What nerve innervates the diaphragm?
Phrenic nerve
131
What nerve innervates the external intercostals?
Intercostal nerves
132
What areas of the brain control breathing?
PONS and medulla
133
What spinal level controls the diaphragm?
C3-5
134
What does the dorsal respiratory root control?
Inspiration
135
What does the ventral respiratory root control?
Expiration and maintain muscle tone in the pharynx, larynx and tongue
136
What is the primary ventilatory drive?
Medulla
137
What signal does the medulla respond to?
H+ ions (indirectly CO2)
138
What do the central chemoreceptors respond to?
CSF H+ concentration
139
Why do central chemoreceptors not respond to plasma H+?
The blood brain barrier is permeable to gases, not ions
140
What do the peripheral chemoreceptors respond to?
Plasma H+ and PO2
141
Where are the peripheral chemoreceptors located?
Carotid and aortic bodies
142
What must PO2 fall below to activate the peripheral chemoreceptors?
60mmHg
143
What does an decrease in blood pH cause?
Increased ventilation
144
What drugs affect respiratory centres?
Barbituates and opioids depress respiratory centres
Gaseous anaesthetics increase respiratory rate but decrease tidal volume and alveolar ventilation
Nitrous oxide blunts peripheral chemoreceptor response
