Respiratory Physiology Flashcards
1
Q
Functions of the respiratory system
A
Gas exchange
Acid base balance
Protection from infection
Communication via speech
2
Q
Main factors affection blood oxygen levels
A
Composition of inspired air
Alveolar ventialtion
Oxygen diffusion between alveoli and blood
Adequate perfusion of alveoli
3
Q
Blood transport of pulmonary artery
A
Away from heart
4
Q
Blood transport of pulmonary vein
A
Towards heart
5
Q
Net volume of gas exchanged in the lungs
A
250ml/min oxygen, 200ml/min carbon dioxide
6
Q
Respiration rate at rest
A
12-18 breaths/min, 40-45 at max.
7
Q
Respiratory system pathway
A
Nose, pharynx, epiglottis, larynx, trachea, bronchus, bronchiole, alveoli
8
Q
Function of nose
A
Warms and moistens air coming in
9
Q
Function of epiglottis
A
Flap over trachea that prevent food entering
10
Q
Function of larynx
A
Voice box that contains vocal chords
11
Q
Division between upper and lower respiratory tract
A
Larynx which is the final structure of upper respiratory tract
12
Q
Structure that maintains the patency of trachea and bronchi
A
C-shaped rings of cartilage
13
Q
Impact of decreasing diameter of airway on airflow resistance
A
Airflow resistance increases. (vv)
14
Q
Alveoli cells
A
Type I and II alveolar cells (pneumocytes) and macrophages
15
Q
Function of type I alveolar cells
A
Gas exchange
16
Q
Function of type II alveolar cells
A
Secrete surfactant
17
Q
Function of elastic fibres of alveoli
A
Stretch during inspiration and coil to squeeze out air during expiration
18
Q
Anatomical dead space
A
Gas in the upper airways that does not participate in gas exchange (150ml)
19
Q
Functions of mucous
A
Moistens air
Traps particles
Provides large surface area for cilia to act on
20
Q
Boyle’s gas law
A
States that the pressure exerted by a gas is inversely proportional to its volume
21
Q
Number of and names of lobes of right lung
A
3 lobes
Superior, middle and inferior
22
Q
Number of and names of lobes of left lung
A
2 lobes
Superior and inferior
23
Q
Pleaural sac components
A
Visceral pleaural membrane, parietal pleural membrane and pleaural fluid
24
Q
Visceral pleural membrane
A
Coats outer surface od the lungs
25
Pariteal pleaural membrane
Coats inner surface of the ribs
26
Pleaural fluid
(5ml)
Allows membranes to glide across each other and reduces friction.
Stops membranes separating so that the lungs are stuck to the rib cage and diaphragm.
27
Muscles of inspiration
External intercostal muscles, diaphragm, scalene and sternocleidomastoids.
28
Muscles of expiration
Internal intercostal muscles and abdominal muscles
29
Movement of gas
From high pressure to low pressure
30
Diaphragm during inspiration
Contacts so that thoracic volume increases
31
Diaphragm during expiration
Relaxes so that thoracic volume decrease.
32
Pump handle motion of intercostals
Increases anterior-posterior dimension of rib cage
33
Bucket handle motion of intercostals
Increases lateral dimension of rib cage.
34
Asthma
Over-reactive constriction of bronchial smooth muscles, increase airway resistance
35
Intra-thoracic (alveolar) pressure
Pressure inside the thoracic cavity. Negative or positive relative to atmospheric pressure
36
Intra-pleaural pressure
Pressure inside pleural cavity. Always negative relative to atmospheric pressure. Created by opposing pulls.
37
Transpulmonary pressure
Difference between alveolar and intra-pleural pressure. Always positive relative to atmospheric pressure
38
Changes of alveolar pressure relative to atmospheric pressure
Inspiration - negative
| Expiration - positive
39
Changes of intra-pleural pressure relative to atmospheric pressure
Inspiration - more negative
| Expiration - less negative
40
Tidal volume
The volume of air breathed out of lungs at each breath - 500ml
41
Expiratory reserve volume
The maximum volume of air which can be expelled from the lungs at the end of a normal expiration - 1100ml
42
Inspiratory reserve volume
The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration - 3000ml
43
Residual volume
The volume of gas in the lungs at the end of a maximal expiration - 1200ml
44
Vital capacity
TV+IRV+ERV - 4600ml
45
Total lung capacity
VC+RV - 5800ml
46
Inspiratory capacity
TV+IRV - 3500ml
47
Functional residual capacity
ERV+RV - 2300ml
48
Ventilation
The movement of air in and out of lungs
49
Pulmonary ventilation
Total air movement in and out of lungs
50
Alveolar ventialtion
Fresh air getting to alveoli and so available for gas exchange
51
Volume of air participating in gas exchange at rest
350 out of 500ml due to anatomical dead space.
52
Factors effecting ventilation
Depth of breathing
| Respiratory rate
53
Dalton's law
States that the total pressure of a gas mixture is the sum of the pressure of the individual gases
54
Partial pressure
The percentage of individual gas in gas mixture multiplied by the total pressure
55
Normal alveolar pressure of oxygen
100mmHg (13.3kPa)
56
Normal alveolar pressure iof carbon dioxide
40mmHg (5.3kPa)
57
Surfactant
Detergent like fluid that reduced surface tension on alveolar surface membrane
58
Surface tension
Attraction of one water molecule to another
59
Effect of surfactant
Reduces tendency for alveoli to collapse
Increases lung compliance
Reduces lung's tendency to recoil
Makes work of breathing easier
60
Reason surfactant more effective in small alveoli
Because surfactant molecules come closer together and are therefore more concentrated
61
Saline
Liquid which inflates lungs in utero - less change in pressure required as do not need to overcome surface tension
62
Compliance
Change in volume relative to change in pressure
63
High compliance
Large increase in lung volume for a small decrease in intra-pleural pressure
64
Low compliance
Small increase in lung volume for a large decrease in intra-pleural pressure.
65
Compliance during inspiration compared to expiration
Lower due to tissue inertia - starting stretch required to open up compressed airways
66
Compliance in emphysema
Reduced as loss of elastic tissue means expiration requires effort
67
Compliance in fibrosis
Reduced due to inert fibrous tissue increasing effort of inspiration
68
Effect of height of alveolar ventilation
Alveolar ventilation declines with height from base to apex
69
Effect of height on compliance
Compliance declines with height from base to apex
70
Obstructive lung disease
Obstruction of air flow through airways, especially on expiration
71
Restrictive lung disease
Restriction of lung expansion
72
Examples of obstructive lung diseases
Asthma
| COPD
73
Examples of restrictive lung diseases
Fibrosis
Infant respiratory distress syndrome (insufficient surfactant production)
Oedema
Pneumothorax
74
Spirometry
Technique commonly used to measure lung function
75
Static spirometry
Only consideration made is the volume exhaled
76
Dynamic spirometry
Time taken to exhale a certain volume is what is being measured
77
Lung volumes that can be measured by spirometry
TV, IRV, ERV, IC, VC - if you can breathe it then spirometry can measure it
78
FEV1
Forced expiratory rate in one second
79
FVC
Forced vital capacity (breathing out as hard as you can)
80
FEV1/FVC ratio in healthy individuals
80%
81
FEV1/FVC in obstructive lung disease
FEV1 reduces greatly
FVC reduces
Ratio decrease
82
FEV1/FVC in restrictive lung disease
FEV1 reduces greatly
FVC reduces greatly
Ratio unchanged
83
Forced expiratory flow
Average expired flow over the middle of an FVC, correlates with FEV1 but changed are generally more striking, 'normal' range is greater
84
Bronchial circulation
Nutritive, from systemic circulation to supply oxygenated blood to airway smooth muscle, nerves and lung tissue
85
Pulmonary circulation
Gas exchange, unique system, supplies dense capillary network surrounding alveoli and returns oxygenated blood.
86
Blood flow in pulmonary circulation
High flow, low pressure
87
What determines the partial pressure of gases in the alveoli
The partial pressure of gases in the arterial blood
88
What determines the partial pressure of gases in the tissues
The partial pressure of gases in the venous blood
89
PAo2
100mmHg
90
PAco2
40mmHg
91
Pao2
100mmHg
92
Paco2
40mmHg
93
Pvo2
40mmHg
94
Pvco2
46mmHg
95
Gas exchange at alveoli
Oxygen moves from alveoli to arterial blood and carbon dioxide moves from venous blood to alveoli.
96
Gas exchange at tissues
Oxygen moves from arterial blood to tissues and carbon dioxide moves from tissues to venous blood.
97
Gases moves between the alveoli, blood and tissue by
Diffusion, down their partial pressure gradient
98
5 factors that effect diffusion rate
Directly proportional to the partial pressure gradient, gas solubility and available surface area. Inversely proportional to the thickness of membrane. More rapid over short distances.
99
Why does carbon dioxide diffuse at the same pace as oxygen despite less volume of movement
Because carbon dioxide is more soluble in water than oxygen - equalises effect of greater pressure difference of oxygen
100
Gas exchange in emphysema
Destruction of alveoli reduces surface area for gas exchange
101
Gas exchange in fibrotic lung disease
Thickened alveolar membrane slows gas exchange
102
Gas exchange in pulmonary oedema
Fluid in interstitial space increases diffusion distance. (CO2 may be normal due to high solubility in water)
103
Gas exchange in asthma
Increased airway resistance decreases airway ventilation - no problem with diffusion.
104
Ventilation-perfusion relationship at apex of lungs
Lower perfusion than ventilation
105
Ventilation-perfusion relationship at base of lungs
Higher perfusion than ventilation
106
Effect of height on perfusion
Perfusion decreases with height from base to apex
107
Effect of decreased ventilation in alveoli
Pco2 increases and Po2 decreases - blood flowing past is not oxygenated, shunt
108
Control mechanism in response to decrease in ventilation
Constriction of arterioles around under ventilated alveoli, blood flow redirected to better ventilated alveoli
109
Effect of decreased perfusion
Alveolar dead space, Po2 increases and Pco2 decreases
110
Control mechanism in response to decrease in perfusion
Pulmonary vasodilation to increase perfusion and mild bronchial constriction to decrease ventilation
111
Shunt
The passage of blood through areas of the lung that are poorly ventilated, opposite of alveolar dead space
112
Alveolar dead space
Alveoli that are ventilated but not perfused
113
Physiological dead space
Alveolar dead space + anatomical dead space
114
How much oxygen per litre dissolves in the plasma
3ml/L
115
Haemoglobin increase oxygen carrying capacity to
200ml/L
116
Arterial pressure oxygen defined as
The oxygen in solution in the plasma
117
The partial pressure of oxygen in determined by
Oxygen solubility and the partial pressure of oxygen in the gaseous phase that is driving oxygen into solution
118
Oxygen demand of resting tissues
250ml/min
119
Actual oxygen delivery to tissues
1000ml/min
120
Percentage of arterial oxygen extracted by peripheral tissues at rest
25% resulting in a 75% reservoir
121
Structure of haemoglobin
4 polypeptide chains (2 alpha, 2 beta) each associated with an iron containing ham group
122
Amount of oxygen that binds to each gram of haemoglobin
1.34ml
123
Oxygen binds to haemoglobin by
Oxygenation (not oxidation)
124
Percentage of haemoglobin in red blood cells is in the form HbA
92%
125
Other forms of haemoglobin
HbA2, HbF, glycosylated
126
Major determinant of the degree to which haemoglobin is saturated with oxygen
Partial pressure of oxygen in arterial blood
127
Haemoglobin saturation is complete after how much contact with alveoli
0.25 seconds
128
Haemoglobin saturation at PaO2 100mmHg
98%
129
Haemoglobin saturation at PaO2 40mmHg
75% (still 75% reserve)
130
Reason why HbF and myoglobin have a higher affinity for oxygen that HbA
Necessary for extracting oxygen from maternal/arterial blood
131
Anaemia
Any condition where the oxygen carrying capacity of the blood is compromised
132
Examples of anaemia
Iron deficiency, haemorrhage, vitamin B12 deficiency
133
Effect of anaemia on PaO2
No change
134
Effect of anaemia on haemoglobin oxygen saturation
No change
135
Factors that effect the affinity of haemoglobin for oxygen
pH, Pco2, temperature and 2,3-DPG
136
Affinity of haemoglobin for oxygen decreased by
Decrease in pH, increase in Pco2, increase in temperature, binding of 2,3-DPG
137
Affinity of haemoglobin for oxygen increased by
Increase in pH, decrease in Pco2, decrease in temperature, no 2,3-DPG
138
2,3-diphosphoglycerate (2.3-DPG) is synthesised by
Erythrocytes
139
When does 2,3-DPG increase and why
When there is inadequate oxygen supply (e.g. high altitudes) to maintain oxygen release in the tissues
140
Affinity of haemoglobin for carbon monoxide compared to oxygen
250 times greater
141
Problem of carbon monoxide
Binds to haemoglobin readily (carboxyhaemoglobin) and dissociates very slowly, prevents oxygen from binding to haemoglobin
142
Hypoxaemic hypoxia
Reduction in oxygen diffusion at lungs
143
Anaemic hypoxia
Reduction in oxygen carrying capacity of blood due to anaemia
144
Stagnant hypoxia
Inefficient pumping of blood to lungs/around the body
145
Histotoxic hypoxia
Poisoning prevent cells utilising oxygen delivered to them
146
Metabolic hypoxia
Oxygen delivery to the tissues does not meet increased oxygen demand by cells
147
Percentage of carbon dioxide that remains dissolved in plasma and erythrocytes
7%
148
Percentage of carbon dioxide that combines in erythrocytes with deoxyhemoglobin
23%
149
Product formed when carbon dioxide combines with deoxyhemoglobin
Carbamino compounds
150
Percentage of carbon dioxide that combines in erythrocytes with water
70%
151
Product formed when carbon dioxide combines with water
Carbonic acid
152
Fate of carbonic acid
Dissociates to yield bicarbonate and hydrogen ions
153
Fate of bicarbonate
Moves out of erythrocytes into the plasma in exchange for chlorine ions
154
Fate of excess hydrogen ions
Bind to deoxyhemoglobin
155
Carbon dioxide is capable of changing ECF pH due to
Production of hydrogen ions when combined and dissociated
156
Ventilatory control resides within
Respiratory centres - ill defined centres in the [os and medulla
157
Ventilatory control in entirely depending on
Signalling from the brain (doesn't have its own rhythmic beat)
158
Respiratory centres function
Set an automatic rhythm for breathing and adjust thus rhythm in response to stimuli
159
Respiratory centres set an automatic rhythm of breathing through
Co-ordinating the firing of smooth and repetitive bursts of action potentials to DRG
160
Dorsal respiratory group (DRG)
Output primarily to inspiratory muscles
161
Ventral respiratory group (VRG)
Output to expiratory muscles, some inspiratory, pharynx, larynx and tongue muscles
162
Pontine respiratory group (PRG)
Contains higher brain centres
163
Respiratory centres have their rhythm modulated by
Emotion, voluntary over-ride, mechano-sensory input from thorax, chemical composition of blood
164
Chemical composition of blood is detected by
Chemoreceptors
165
Central chemoreceptors
In medulla, respond directly to hydrogen ions, primary ventilation drive
166
Peripheral chemoreceptors
Carotid and aortic bodies, respond primary to plasma hydrogen ion concentration and PO2, secondary ventilatory drive
167
Hypercapnea
Raised Pco2
168
Central chemoreceptors detect changes in hydrogen ion concentration in
Cerebral spinal fluid around brain
169
Central chemoreceptors cause a reflex stimulation of ventilation following
A decrease in arterial Pco2
170
What can and can't pass blood brain barrier
Gas can (carbon dioxide), ions can't (hydrogen ions)
171
Effect of chronic lung disease on chemoreceptors
Pco2 is chronically elevated, central chemoreceptors become desensitised to Pco2, have to rely on peripheral chemoreceptors and changed in Po2 to stimulate ventilation - hypoxic drive
172
Peripheral chemoreceptors cause a reflex stimulation of ventilation following
A significant fall in arterial Po2 or a rise in hydrogen ion concentration
173
Peripheral chemoreceptors will only cause stimulation if oxygen partial pressure falls below
60mmHg
174
Effect of fall of plasma pH on ventilation
Ventilation will be stimulated and vv
175
Reason why respiration is inhibited during swallowing
To avoid aspiration of food or fluids into the airways
176
Common drugs that affect respiratory centres
Barbiturates, opioids, gaseous anaesthetics, nitrous oxide
