Respiratory (summary sheets) Flashcards
(486 cards)
1
Q
What are the components of the upper respiratory tract?
A
- The nose
- Turbinates/Conchae create
- Paranasal sinuses
- Pharynx
- Larynx
2
Q
What is the most superior portion of the respiratory tract?
A
The nose
3
Q
What are the functions of the nose?
A
- Warms inspired air
- Humidifies air
- Filters inspired air of pathogens
- Defence function
4
Q
How does the nose filter inspired air of pathogens?
A
Using cilia in the nose which traps particulates
5
Q
How does the defence function of the nose work?
A
Cilia take inhaled particulates backwards to be swallowed
6
Q
What do the anterior nares do in relation to the defence function of the nose?
A
Opens into the enlarge vestibule (skin lined and has stiff hairs)
7
Q
What gives the nose a large surface area?
A
It is doubled by turbinates
8
Q
What are the 3 turbinates/ conchae create?
A
Superior meatus, middle meatus and inferior meatus
9
Q
Give 3 features of the superior meatus
A
- Has olfactory epithelium
- Olfactory nerve penetrates into superior meatus through pores in the cribriform plate
- Sphenoid sinus drains into it
10
Q
Give a feature of the middle meatus
A
Some sinuses drain here
11
Q
Give a feature of the inferior meatus
A
Nasolacrimal duct drains there
12
Q
Give 2 features of the paranasal sinuses
A
- Pneumatised areas (a bone that is hollow or contains many air cells) of the frontal, maxillary, ethmoid and sphenoid bones
- Arranged in pairs
13
Q
Give 2 features of the frontal sinuses
A
- Within the frontal bone
- Lie over the orbit
14
Q
Where are the maxillary sinuses located?
A
Within the body of the maxilla
15
Q
Which nerve innervates the frontal sinuses?
A
The ophthalmic division of the trigeminal nerve (CN5)
16
Q
What shape is the maxillary sinus?
A
Pyramidal
17
Q
Which nerve innervates the maxillary sinus?
A
The maxillary division of the trigeminal nerve (CN5)
18
Q
Where does the base of the maxillary sinus lie?
A
The lateral wall of the nose
19
Q
Where does the apex of the maxillary sinus lie?
A
Zygomatic process of the maxilla
20
Q
Where does the roof of the maxillary sinus lie?
A
Floor of the orbit
21
Q
Where does the floor of the maxillary sinus lie?
A
Alveolar process
22
Q
Where does the maxillary sinus open into?
A
The middle meatus
23
Q
Where is the ethmoid sinuses?
A
Between the eyes
24
Q
Which nerve innervates the ethmoid sinuses?
A
The ophthalmic and maxillary branches of the trigeminal nerve (CN5)
25
Where do the ethmoid sinuses open into?
The middle meatus
26
Where is the sphenoid sinuses?
Medial to the cavernous sinus and inferior to optic canal, dura and pituitary gland
27
Name the artery and the 4 cranial nerves which are in the cavernous sinus
- Internal carotid artery
- Oculomotor never (CN3)
- Trochlear nerve (CN4)
- Trigeminal nerve (CN5)
- Abducens (CN6)
28
What is the importance of keeping the cavernous sinus functioning?
Contains many important structures, nerves for eye movement and heart blood supply
29
Where do the sphenoid sinuses empty into?
The sphenoethmoidal recess, lateral to the attachment of the nasal septum
30
Which nerve innervates the sphenoid sinus?
The ophthalmic branch of the trigeminal nerve (CN5)
31
The sphenoid sinus is close to which gland?
The pituitary gland
32
What is the pharynx?
A fibromuscular tube which takes filtered air from the nose to larynx
33
What are the cell types in the pharynx?
Squamous and columnar ciliated epithelium
34
Where is the pharynx?
Extends from the skull base to C6, where is becomes continuous with the oesophagus
35
What are the three components of the pharynx?
Nasopharynx, oropharynx, laryngopharynx
36
What is the valvular function of the larynx?
Prevents liquids and food from entering the lungs
37
What is the structure of the larynx?
- Rigid structure
- Has 9 cartilages
- Has multiple muscles
38
What are the 3 paired cartilages in the larynx?
Cuneiform, corniculate and arytenoid
39
What are the 3 unpaired cartilages in the larynx?
Epiglottis, thyroid and cricoid
40
What is the significant feature of the arytenoid cartilages?
Rotate on the cricoid cartilage to change the vocal chords
41
What nerve innervates the larynx?
The vagus nerve (CN10) - superior laryngeal and recurrent laryngeal nerve
42
What are the divisions of the superior laryngeal nerve and what are their functions?
- Internal (for sensation)
| - External (motor innervation to the cricothyroid muscle)
43
What is the function of the recurrent laryngeal nerve?
Provides motor innervation for all muscles except the cricothyroid muscle
44
Where does the left recurrent laryngeal nerve run?
Runs laterally to the arch of the aorta, loops under aortic arch, ascends between the trachea and oesophagus
45
Where does the right recurrent laryngeal nerve run?
Loops under the right subclavian artery, then runs up plane between trachea and oesophagus
46
What is a sign of a tumour/ulcer on/near the recurrent laryngeal nerve?
Hoarse voice
47
What are the components of the lower respiratory tract?
- Trachea
- Main Bronchi
- Lobar bronchi
- Segmental branches
- Alveoli
48
What is the main function of the lungs?
Gas exchange
49
What is the gas exchange area per lung?
20 m^2 per lung
50
Define minute volume
The volume of air inhaled/exhaled in a minute
51
Define cardiac output
Volume of blood pumped out by the heart a minute
52
What is the approx value for the minute volume?
5 litres
53
What is the approx value for the cardiac output?
5 litres
54
Where is the trachea?
From larynx to carina (C6-T5)
55
What shape is a cross section of the trachea?
Oval
56
What structure is the cartilage in the trachea?
Semi-circular C-shaped hyaline cartilage connected by tracheal muscle
57
How come the cartilage in the trachea is C-shaped?
Increases the flexibility of the trachea
58
What are the cell types in the trachea?
Pseudo-stratified ciliated columnar epithelium
59
Name a cell type which is present in the trachea?
Goblet cells
60
Which is more mobile: upper trachea or distal trachea?
Upper trachea
61
What is the carina?
A ridge of cartilage in the trachea that occurs between the division of the two main bronchi
62
Where does the main bronchi divide into a left and right bronchus?
At the carina, at the level of T5
63
Which bronchus is more vertically disposed?
The right main bronchus
64
How long is the right main bronchus?
1-2.5 cm long
65
Which artery is the right main bronchus related to?
Right pulmonary artery
66
Which bronchus comes off at more of an angle?
Left main bronchus
67
How long is the left main bronchus?
5cm
68
Which artery is the left main bronchus related to?
Aortic arch
69
Which bronchus are things more likely to get stuck in and why?
Right - due to the left being longer and more angled
70
How many lobes are there in the right lung and what are their names?
3 - upper, middle and lower
71
How many lobes are there in the left lung and what are their names?
2 - upper and lower
72
How does the lobar bronchi divide in the right lung?
3 divisions
73
How does the lobar bronchi divide in the left lung?
2 divisions
74
How many segmental branches are there in the right lung?
10
75
How many segmental branches are there in the left lung?
8
76
What are the divisions after the lobar bronchi?
- Terminal bronchioles
- Respiratory bronchioles
- Alveolar ducts (short tubes with multiple alveoli)
- Alveoli
77
What is a acinus of the lung?
The tissue supplied with air by one terminal bronchiole
78
What are the 6 cell types present in the alveoli?
- Type I pneumocytes
- Type II pneumocytes (secrete surfactant)
- Alveolar macrophages
- Basement membrane
- Membrane 1 micron thick
- Columnar ciliated epithelium
79
Where does the pulmonary plexus lie?
Behind each hilum
80
What does the pulmonary plexus receive innervation from?
- The right and left vagus (CN10)
| - The T2-T4 ganglia of the sympathetic trunk
81
What does sympathetic supply cause in the lung?
- From the sympathetic trunk
| - Results in bronchodilation
82
What does parasympathetic supply cause in the lung?
- From the vagus
| - Results in bronchoconstriction
83
Why is the right lung larger than the left?
Due to the silhouette of the heart
84
How many lobes does the right lung have?
3
85
What are the names of the lobes of the right lung?
Superior, middle and inferior
86
How many lobes does the left lung have?
2
87
What are the names of the lobes of the left lung?
Superior and inferior
88
What is lung pleura and what are the layers?
- 2 main layers of mesodermal origin
- Visceral and parietal layer s
- Each a single layer of cells
89
Where does the visceral layer of the lungs lie?
Applied to the lung surface - only have autonomic innervation
90
Where does the parietal layer of the lungs lie?
Applied to the internal chest - has pain sensation via phrenic nerve
91
Where are the layers of the lung pleura continuous?
At the lung root
92
What are the two blood supplies of the lungs?
Bronchial and pulmonary
93
What vessels are involved in the pulmonary circulation?
- Left and right pulmonary arteries run from the right ventricle
- Bronchus & pulmonary arteries run together - via the bronchovascular bundle
- Pulmonary veins run on their own
94
What is the standard minute volume (lungs)?
5 litres of air a minute
95
Define transpulmonary pressure
Difference in pressure between the inside and outside of the lung (alveolar - intrapleural pressure)
96
Define intrapleural pressure
The pressure in the pleural space, also known as intrathoracic pressure
97
Define alveolar pressure
Air pressure in pulmonary alveoli
98
What is inspiration initiated by?
A neurally induced contraction of the diaphragm and the external intercostal muscles located between the ribs
99
What is the most important inspiratory muscle during normal quiet breathing?
The diaphragm
100
Where are the impulses stimulating contraction of the diaphragm from?
Via the phrenic nerve, arises from C3, 4 & 5 (C345 keeps the diaphragm alive)
101
What does the diaphragm do during inspiration?
- Contracts causing its dome to move downwards
| - Enlarges the thorax so increasing the volume
102
What happens to the intercostal muscles during inspiration?
- Activation of the motor neurones in the intercostal nerves to the EXTERNAL intercostal muscles
- Causes contractions
- Results in an upward and outward movement of the rib (further increase in thoracic volume)
103
What happens as the thorax expands during inspiration?
- The intrapleural pressure is being lowered and the transpulmonary pressure is becoming more positive
- Results in lung expansion as transpulmonary pressure > elastic recoil of lungs
- Lung expansion results in the alveolar pressure becoming negative and results in an inward flow
104
What causes the end of the inspiration?
- The chest wall is no longer expanding but yet to start passive recoil as lungs remain the same size
- The glottis is open
- Alveolar pressure = atmospheric pressure
- Results in no airflow
105
When does expiration occur?
At the end of inspiration
106
What happens to the intercostal muscles at the end of inspiration/start of expiration?
- The motor neurones to the diaphragm and external intercostal muscles decrease their firing
- These muscles can relax
- Diaphragm lowers and flattens
- Decreases thoracic volume
107
What happens as the diaphragm and intercostal muscles relax during expiration?
- The lungs and chest walls start to passively collapse due to elastic recoil
- Muscle relaxation causes the intrapleural pressure to increase, so decreasing the transpulmonary pressure, eventually causing passively collapsing
108
What happens as the lungs become smaller during expiration?
Air in the alveoli becomes temporarily decompressed resulting in an increase in alveolar pressure
109
Why is expiration at rest passive?
Due to it only relying on relaxation of the external intercostal muscles and diaphragm and the elastic recoil of the lungs
110
What happens during forced expiration?
- The internal intercostal muscles also contract, along with the abdominal muscles
- This results in the ribs moving downwards and inwards - actively decreasing thoracic volume, increasing intra-abdominal pressure, forcing the relaxed diaphragm further up, further decreasing thoracic volume
111
What is the airway with the greatest resistance and why?
The trachea - has a small surface area meaning it provides more resistance
112
Define dead space
The volume of air not contributing to ventilation
113
Where does gas exchange take place?
Between the alveoli and capillaries
114
What does bulk from in the airways allow for?
Oxygen and carbon dioxide movement - requires a large surface area with minimal distance for gases to move across and adequate perfusion of blood
115
Where do terminal bronchioles lead to?
Respiratory bronchioles, which lead to alveolar ducts & alveoli
116
Where are the respiratory bronchioles found?
In the centre of the acinus
117
What is the total combined area for gas exchange?
40-100m^2
118
How many alveoli are there per lung?
300 million
119
How many capillaries are there per alveolus?
1000
120
How many layers does the oxygen have to diffuse through to get to the erythrocyte?
- 7
- Alveolar epithelium
- Tissue interstitium
- Capillary endothelium
- Plasma layer
- Red cell membrane
- Red cell cytoplasm
- Haemoglobin binding
121
How can the alveoli be the most efficient?
If the correct proportion of alveolar airflow (ventilation) and capillary blood flow (perfusion) shows to be available at each alveolus
122
What is the main effect of ventilation-perfusion inequality?
The partial pressure of oxygen is decreased in systemic-arterial blood
123
What is the natural ventilation-perfusion caused by?
- Gravitational effects
- The upright posture causes the increase of filling of blood vessels at the bottom of the lung (due to gravity)
- This contributes to the difference in blood-flow distribution in the lung
124
What are the two extremes as a direct consequence of V/Q mismatch?
- Ventilated alveoli but no blood supply at all (dead space/wasted ventilation)
- Adequate blood flow through the areas of the lung but there is no ventilation (shunt) due to collapsed alveoli
125
What is the mechanism of hypoxic pulmonary constriction?
- A decrease in ventilation within a group of alveoli - as a result of a mucous plug blocking the small airways
- This decrease in the partial pressure of O2 in the alveoli and nearby blood vessels leads to VASOCONSTRICTION - diverting blood away from the poorly ventilated area
- This effect is unique to the pulmonary arterial vessels (since in systemic circulation the opposite would occur) - it ensures that blood flow is directed away from diseases areas of the lung toward areas that are well-ventilated
126
What is the effects of hypoxic pulmonary constriction unique to and why?
The pulmonary arterial vessel (since in systemic circulation the opposite would occur)
127
What is the mechanism of local bronchoconstriction?
- If there is a decrease in blood flow within a lung region, for example, a small blood clot in a pulmonary arteriole
- The local decrease in blood flow will mean there is less systemic CO2 in the area, resulting in a local decrease of the partial pressure of CO2
- This results in BRONCHOCONSTRICTION which diverts airflow away to areas of the lung with better perfusion
128
What is used to greatly improve the efficiency of pulmonary gas exchange?
Hypoxic pulmonary constriction & local bronchoconstriction
129
What is PaCO2?
Arterial CO2
130
What is PACO2?
Alveolar CO2
131
What is PaO2?
Arterial O2
132
What is PAO2?
Alveolar O2
133
What is PIO2?
Pressure of inspired O2
134
What is VA?
Alveolar ventilation
135
What is VCO2?
CO2 production
136
What is the structure of a haemoglobin molecule?
- Protein made up of 4 subunits bound together
- Each subunit is a heme group and a polypeptide attached
- The 4 polypeptides of the molecule are called globin
- Each of the four heme groups contain one atom of iron to which molecular oxygen binds
137
What are the two forms that haemoglobin can exist in?
- Hb (deoxyhaemoglobin)
| - HbO2 (oxyhemoglobin)
138
Why is the oxygen-dissociation curve sigmoid shaped?
- Each haemoglobin contains 4 sub-units
- Each subunit can combine with 1 molecule of oxygen
- The reactions occur sequentially
- The binding between oxygen and haemoglobin increases very rapidly as the partial pressure of oxygen is increased
139
Where does haemoglobin give up its oxygen?
In areas of low partial O2 pressure (e.g. metabolically active tissue) where oxygen will diffuse from an area of high concentration to an area of low concentration
140
What does an increase in temperature do to the oxygen-dissociation curve?
Cause the curve to shift to the right
141
What does a shift to the right on the oxygen-dissociation curve mean?
Haemoglobin has less affinity for oxygen
142
What does a decrease in pH do to the oxygen-dissociation curve?
Cause the curve to shift to the right
143
What does a decrease in temperature do to the oxygen-dissociation curve?
Cause the curve to shift to the left
144
What does a shift to the left on the oxygen-dissociation curve mean?
Haemoglobin has more affinity for oxygen
145
What does an increase in pH do to the oxygen dissociation curve?
Cause the curve to shift to the left
146
What kind of temperature increase will shift the oxygen-dissociation curve?
Because of heat produced by tissue metabolism
147
What kind of pH decrease will shift the oxygen-dissociation curve?
Because of elevated CO2 partial pressure (which enters from the tissues) and the release of metabolically produced acids
148
What happens when haemoglobin is exposed to elevated partial CO2 pressure, reduced pH and increased temperatures?
- As it passes through the tissue capillaries it has a decreased affinity for oxygen
- Means it gives up more oxygen
149
What factors about a metabolically active tissue causes a greater oxygen release?
- Greater partial CO2 pressure
- Lower pH
- Greater temperature
- Releases more oxygen so to provide more active cells with additional oxygen
150
What does carbon monoxide do to the oxygen dissociation curve?
Shifts it to the left, so decreasing the unloading of oxygen from haemoglobin in the tissues
151
What is the equation which links arterial CO2 and alveolar ventilation?
PaCO2 = (k x VCO2)/ VA
152
What are the three ways in which carbon dioxide is carried in the blood?
- Bound to haemoglobin
- Dissolved in plasma
- As bicarbonate
153
What does carbon dioxide binding to haemoglobin form?
Carbaminohaemoglobin - deoxygenated haemoglobin has a greater affinity for carbon dioxide than oxygen
154
How is bicarbonate formed in the erythrocyte?
- Produced with the enzyme carbonic anhydrase in the erythrocyte
- Rapid dissociation into bicarbonate and H ion
- Bicarbonate moves into the plasma from the erythrocyte via a transporter, which exchanges one bicarbonate for one chloride ion
- Bicarbonate leaving the erythrocyte favours the forward reaction
155
What happens to the remaining hydrogen ion from bicarbonate formation in the erythrocyte?
- Binds to deoxyhaemoglobin
- As venous blood passes through the lungs, deoxyhaemoglobin becomes converted to oxyhemoglobin
- In the process, releases the H picked up in the tissues
- This reacts with bicarbonate to produce carbonic acid
- Carbonic anhydrase dissociates this to from CO2 & H2O
- CO2 then diffuses to the alveoli to be expired
156
What happens when venous blood reaches the lungs?
- The blood partial CO2 pressure is higher than alveolar partial CO2
- A net diffusion of CO2 from the blood to the alveoli occurs
- The loss of CO2 causes H ions and bicarbonate to produce H2CO3, which then dissociate back into CO2 & H2O
157
Why are the bodies acids and bases regulated?
The ensure for optimal function e.g. for enzymes
158
What is the normal pH of the blood?
Around 7.4 (7.35-7.45)
159
How is the acid-base balance regulated?
By mechanisms which generate, buffer and eliminate acids and bases
160
Are the bodies acids and bases weak or strong?
Weak
161
How is the pH of bodily fluids maintained?
- Intracellular & extracellular buffers
- The lungs eliminating CO2
- Renal bicarbonate reabsorption and hydrogen ion elimination
162
What is the most important buffer in the body?
- The carbonic acid/bicarbonate buffer
| - Works with the lungs to compensate for increased carbonic acid production
163
What is the phenomenon which occurs when a person HYPOventilates?
- Inadequate ventilation of the alveoli
- CO2 can't be excreted and expired adequately
- Partial pressure of CO2 increases thereby resulting in more carbonic acid being produced
- Increased hydrogen ion conc. in the blood
- RESPIRATORY ACIDOSIS
164
What is the phenomenon which occurs when a person HYPERventilates?
- Decrease arterial partial CO2 pressure
- Decreased hydrogen ion conc. in the blood
- RESPIRATORY ALKALOSIS
165
What is the Henderson-Hasselbach equation?
- pH = 6.1 + log10([HCO3-]/[0.03 x PCO2])
- 6.1 is the dissociation constant for the bicarbonate buffer system
- 0.03 x PCO2 is an estimate of H2CO3
- 0.03 = the blood carbon dioxide solubility co-efficient
166
What is Dalton's law?
- Pressure exerted by each gas in a mixture is independent of the pressure exerted by other gases
- This is due to gas molecules being so far apart from each other
- Total pressure = sum of partial pressures
- Partial pressures are directly proportional to its concentration
167
What is Boyle's law?
- Pressure of a fixed amount of gas in a container is inversely proportional to container's volume
- P1V1 = P2V2
168
What is Henry's law?
- Amount of gas dissolved in a liquid is proportional to the partial pressure of gas with which the liquid is in equilibrium
- At equilibrium the partial pressures of the gas molecules in the liquid and gaseous phases must be identical
169
What is the alveolar gas equation?
- PAO2 = PiO2 - PaCO2/R
| - R = the respiratory exchange ratio - the ratio between the amount of CO2 produced in metabolism and oxygen used
170
How is pressure in the bronchi calculated?
Pressure = flow x resistance
171
What is the law of Laplace?
- Describes the relationship between pressure (P), surface tension (T) and the radius (r) of an alveolus
- P = 2T/r
172
What is lung compliance?
- The change in lung volume caused by a given change in transpulmonary pressure
- The greater the lung compliance, the more readily the lungs are expanded
173
Name two determinants of lung compliance
- Stretchability of the lung tissues
| - Surface tension of the air-water interfaces of the alveoli
174
How does the stretchability of the lung tissues affect lung compliance?
A thickening and thus a loss in stretchability of the lungs elastic connective tissue results in a decrease in lung compliance
175
How does surface tension of the air-water interfaces of the alveoli affect lung compliance?
- The surface of alveolar cells are moist, thus alveoli are effectively air-filled sacs lined with water
- At the interface, attractive forces between the water molecules (surface tension), makes the water lining like a stretched balloon that constantly tends to shrink and resists further stretching
- The expansion of the lungs requires energy not only to expand the connective tissues, but to overcome surface tension of the water layer lining the alveoli
176
What is the function of the type II pneumocytes and why is this important?
- Produces surfactant
- This reduces the cohesive forces between water on the alveolar surface
- Lowers the surface tension, so increases lung compliance and makes it easier to expand the lungs
177
When does the amount of surfactant tend to decrease?
When breaths are small and constant
178
What does a deep breath do in terms of surfactant production?
- Stretches type II pneumocytes
| - Stimulates the secretion of surfactant
179
Define inspiratory reverse volume
Amount of air in excess tidal inspiration that can be inhaled with maximum effort
180
Define expiratory reverse volume
Amount of air in excess tidal expiration that can be exhaled with maximum effort
181
Define residual volume
Amount of air remaining in the lungs after maximum expiration; keeps alveoli inflated between breaths and mixes with fresh air on next inspiration
182
Define vital capacity
Amount of air that can be exhaled with maximum effort after maximum inspiration (ERV + TV + IRV); used to assess strength of thoracic muscles as well as pulmonary function
183
Define functional residual capacity
Amount of air remaining in the lungs after a normal tidal expiration (RV + ERV)
184
Define inspiration capacity
Maximum amount of air that can be inhaled after a normal tidal expiration (TV + IRV)
185
Define total lung capacity
Maximum amount of air the lungs can contain (RV + VC)
186
Define tidal volume
Amount of air inhaled or exhaled in one breath
187
What is the process for a FEV1 reading?
In which a person takes a maximal inspiration and then exhales maximally as fast as possible. The important value is the fraction of the total “forced” vital capacity expired in 1 second
188
What is the approximate amount that a healthy individual can expire in 1 second?
80% of vital capacity
189
What is the pattern of flow of the breath?
Greatest at the start of expiration, it declines linearly with volume
190
Define FEF25
Flow at point when 25% of total volume to be exhaled has been exhaled
191
Define FVC
Forced vital capacity, the total amount of air forcibly expired
192
How is FEV1 used to detect for abnormal values?
- Result is compared with the predicted values if the FEV1 is 80% of greater than the predicted value = normal
- If the FEV1 is less than 80% of the predicted value = Low
193
How is FVC used to detect for abnormal values?
- Result is compared with the predicted values, if the FVC is 80% or greater than the predicted = normal
- If the FVC is less than 80% of the predicted value = low
194
How does a low FVC mean?
Airways restriction
195
What is the FEV1/FVC ratio?
- The proportions of FVC exhaled in the 1st second
| - FEV1 is divided by FVC
196
How can the FEV1/FVC ratio be used to detect for abnormal values?
- If the ratio is below 0.7 = airway obstruction
| - If the ratio is high (normal) but the FVC is low = airway restriction
197
What does a low FEV1/FVC ratio mean?
Airway obstruction
198
What does a high FEV1/FVC ratio but a low FVC mean?
Airway restriction
199
What is inspiration initiated by?
A burst of action potentials in the spinal motor neurones to inspiratory muscles like the diaphragm (the vagus nerve arises from C3, 4 & 5 for the diaphragm)
200
How does expiration occur due to the nervous system?
- Action potentials cease
- Inspiratory muscles relax
- Expiration occurs as the elastic lungs recoil
201
Where does control of breathing primarily reside?
In the neurones of the medulla oblongata (the same area of the brain that contains the major cardiovascular control centres)
202
What are the two main anatomical components of the medullary respiratory centre?
- The neurones of the dorsal respiratory group (DRG)
| - The neurones of the ventral respiratory group (VRG)
203
What is the function of the dorsal respiratory group?
These primarily fire during inspiration and have input to the spinal motor neurons that activate respiratory muscles involved in inspiration - diaphragm and external intercostal muscles
204
What is the function of the ventral respiratory group?
- The other main complex of neurones in the respiratory centre
- Contains expiratory neurones that appear to be most important when large increases in ventilation are required
- During active expiration, motor neurones activated by the expiratory output of the VRG cause the expiratory muscles to contract
- During quiet breathing the respiratory rhythm generator activates inspiratory neurons in the VRG that depolarise the inspiratory spinal motor neurons, resulting in the inspiratory muscles contracting
205
Where is the respiratory rhythm generator located?
The pre-Botzinger complex of neurones in the upper part of the VRG
206
What is the structure and function of the respiratory generator
Composed of pacemaker cells and a complex neural network that, acting together, set the basal respiratory rate
207
Where does the medullary inspiratory neurones receive impulses from?
- Receive a rich synaptic input from neurones from various areas in the pons
208
Where is the pons located?
Part of the brainstem, just above the medulla
209
What is the function of the apneustic centre?
- Involved in fine tuning the output of the inspiratory neurones of the medulla
- In continuing to active inspiratory neurones to inhibit expiration
210
What can override the apneustic centre when related to respiration?
The pneumotaxic centre
211
Where is the apneustic centre located?
The lower pons
212
What is the function of the pneuotexic centre?
- Regulates and may override the activity of the apneustic centre
- Acts to smooth the transition between inspiration and expiration
- Also involved in switching off inspiratory neurones to prevent hyper inflation, so allowing expiration
213
Where is the pneumotaxic centre located?
The upper pons
214
What are the receptors which are present in the nose, nasopharynx and larynx and what are their functions?
- Chemo and mechano receptors
- Some appear to sense and monitor flow
- Stimulation of these receptors appears to inhibit the central controller
215
What are the receptors which are present in the pharynx and what are their functions?
- Appear to be activated by swallowing
| - Respiratory activity stops during swallowing thereby protecting against the risk of aspiration of food or liquid
216
What is the function of slowly adapting stretch receptors?
- Maintain a persistent or slowly decaying receptor potential during constant stimulus
- Initiating action potentials in afferent neurones for the duration of the stimulus
- Myelinated
217
Where are slowly adapting stretch receptors found?
In airways smooth muscle
218
What activates the slowly adapting stretch receptors?
Lung distension
219
What happens when there is high activity of the slowly adapting stretch receptors?
- Inhibits further inspiration, thus beginning expiration
| - If inflammation is maintained they slowly adapt to low frequency firing
220
What is the function of rapidly adapting stretch receptors?
- Generate a receptor potential and action potentials at the onset of a stimulus but very quickly cease responding
- Myelinated
221
Where are rapidly adapting stretch receptors found?
Between airway epithelial cells
222
What activates rapidly adapting stretch receptors?
Lung distension and irritants
223
What happens to the rapidly adapting stretch receptors when there is high activity?
- High activity causes bronchoconstriction
- Produce a brief burst of activity
- May be involved in the cough reflex
224
Where are the C-fibre J receptors found?
- In either the capillary walls or the interstitium
| - Non-myelinated
225
What stimulates the C-fibre J receptors?
- An increase in lung interstitial pressure caused by the collection of fluid in the interstitium
- Mainly caused by a pulmonary embolism or left ventricular heart failure
226
What does activity of the C-fibre J receptors cause?
Rapid breathing, shallow breathing, bronchoconstriction, cardiovascular depression and a dry cough
227
What does neural input from J receptors give?
Gives rise to sensation of pressure in the chest and the feeling that breathing is difficult
228
What chemoreceptors mainly give rise to the automatic control of ventilation at rest?
Peripheral (arterial) and central chemoreceptors
229
Where are the peripheral chemoreceptors located?
- High in the neck at the bifurcation of the common carotid arteries
- In the thorax on the arch of the aorta
- Carotid bodies and aortic bodies
230
Where are the peripheral chemoreceptors located close to?
The arterial baroreceptors and are in intimate contact with arterial blood
231
How are the carotid bodies strategically located?
To monitor oxygen supply to the brain
232
What are the peripheral chemoreceptors composed of?
- Specialised receptor cells
| - Type II cells
233
What is the function of the specialised receptor cells of the peripheral chemoreceptors?
- Stimulated mainly by a decrease in the arterial partial pressure of oxygen
- Also by an increase in the arterial H ion concentration
234
What is the function of type II cells of the peripheral chemoreceptors?
- On detection of hypoxia they release stored neurotransmitters that stimulate the carotid sinus nerve
- These cells provide excitatory synaptic input to the medullary inspiratory neurones
235
What is the predominant peripheral chemoreceptor involved in the control of respiration?
The carotid body
236
Are peripheral chemoreceptors sensitive to small reductions of the arterial partial oxygen pressure?
No - its only when there is a large dip when they become sensitive
237
Where are the central chemoreceptors located?
The medulla
238
What is the function of the central chemoreceptors?
Provide excitatory synaptic input into the medullary inspiratory neurones
239
What are the central chemoreceptors stimulated by?
- An increase of hydrogen ions of the CSF
- As the blood-brain barrier is pretty impermeable to H+, changes to the H+ in the blood are poorly reflected in the CSF
- However, CO2 readily diffuses into the CSF and blood partial pressure CO2 influences the H+ levels, enabling the central chemoreceptors to detect changes
240
What happens if there is an increase in arterial partial CO2 pressure?
- Some of the extra CO2 will diffuse into the CSF
- Bicarbonate and hydrogen ions will form in the CSF
- More H ions - enables the central chemoreceptors to detect pH change
- Increase in ventilation by stimulating the medullary inspiratory neurones
241
Define hypoxia
A deficiency of oxygen at the tissue level
242
What is the most common type of hypoxia?
Hypoxemia - in which the arterial partial O2 pressure is reduced
243
What are the most common causes of hypoxia?
- Hypoventilation
- Diffusion impairment
- Shunting
- Ventilation perfusion mismatch
244
What is hypoventilation and what does it cause?
- Results in an increased arterial partial CO2 pressure
- Failure to ventilate the alveoli properly
- Caused by muscular weakness (MND), obesity and loss of respiratory drive
245
What is diffusion impairment and what does it cause?
- Results from the thickening of the alveolar membranes or a decrease in their SA
- Causes the blood partial O2 pressure and alveolar partial O2 pressure to not equilibrate
- Caused by pulmonary oedema, anaemia and interstitial fibrosis
246
What is shunting and what does it cause?
- An anatomical abnormality of the cardiovascular system that causes mixed venous blood to bypass ventilated alveoli in passing from the right side of the heart to the left side
- An intrapulmonary defect in which mixed venous blood perfuses unventilated alveoli
247
What is ventilation-perfusion mismatch and what does it cause?
- Occurs in COPD
- Arterial partial CO2 pressure may be normal or increased
- Can be caused by a pulmonary embolism, asthma, pneumonia & pulmonary oedema
248
What is the most common cause of hypoxemia?
Ventilation-perfusion mismatch
249
Define hypercapnia
Carbon dioxide retention and an increased arterial partial CO2 pressure
250
What is the principle cause of hypercapnia?
- Hypoventilation
| - Can sometimes be caused by ventilation-perfusion mismatch depending on how much ventilation is stimulated
251
What are the features of type I respiratory failure?
- pO2 is low
- pCO2 is low or normal
- With type I = 1 change
252
What is the most common cause of type I respiratory failure?
Pulmonary embolism
253
What are the features of type II respiratory failure?
- pO2 is low
- pCO2 is high
- With type II = 2 changes
254
What is the most common cause of type II respiratory failure?
Hypoventilation
255
What is the unique dual blood supply of the lungs?
The pulmonary circulation (the main circulation) & the bronchial circulation
256
Where does the pulmonary circulation come from?
The right ventricle
257
What percentage of the cardiac output does the pulmonary circulation get from the right ventricle
100%
258
What is the erythrocyte transit time in the pulmonary circulation?
5 seconds
259
How many capillaries is there in the pulmonary circulation?
280 billion
260
What percentage of the left ventricular output does the bronchial circulation get?
2%
261
What are 3 features of the pulmonary artery?
- Vessel wall is thin
- Minor muscularisation
- No need for redistribution
262
What are 3 features of a systemic (everywhere except pulmonary) artery?
- Vessel wall is thick
- Significant muscularisation
- Redistribution is required
263
Which system has a greater pressure - pulmonary or systemic?
Systemic
264
What does the autonomic system compromise of?
- The parasympathetic (normal physiological conditions, rest & digest)
- The sympathetic (fight or flight)
- The enteric (GI tract)
265
What components of the autonomic system serve most organs?
The sympathetic and parasympathetic
266
What is the neurotransmitter of the parasympathetic nervous system?
Acetylcholine
267
How does the parasympathetic nervous system innervate the lungs?
Via the vagus
268
What does the vagus innervate in the lungs?
The vasculature, glands and airways
269
What is the intrinsic tone of airways of the lungs governed by?
The parasympathetic system
270
How does acetylcholine interact with the lungs?
Interacts with the muscarinic cholinergic receptors on the muscle to provide a general level of intrinsic muscle tone
271
What does too much parasympathetic activation of the lungs cause?
Bronchoconstriction
272
What is the neurotransmitter of the sympathetic nervous system?
Noradrenaline
273
How does the sympathetic nervous system innervate the lungs?
Via the sympathetic trunk
274
What does the sympathetic nervous system innervate in the lungs?
The vasculature and the glands
275
What is the indirect influence of the sympathetic system on airways tone?
- Sympathetic activation caused Nad to be released to the adrenal glands
- Can result in the release of adrenaline (from the adrenal medulla)
- This binds to the beta-2-adrenoreceptors on the muscles of the airways
- Results in bronchodilation
276
What are cholinergic neurones?
Neurones which release acetylcholine
277
What is the link with neurones and Alzheimer's?
Neurones associated with the ACh system degenerate in people with Alzheimer's
278
What do nicotinic receptors respond too?
ACh & Nicotine
279
What are nicotinic receptors stimulated by?
Both sympathetic and parasympathetic - but mainly the latter
280
Where are nicotinic receptors found?
In post-ganglionic receptors & in the neuro-muscular junction
281
How does the depolarisation if the nicotinic receptors work?
- Contains a ligand-gated channel which is permeable to both Na and K ions, but as Na has a larger electrochemical driving force, the net effect of opening these channels is depolarisation
282
Is the muscarinic receptor sympathetic or parasympathetic?
Parasympathetic
283
How many types of muscarinic receptors are there?
- 5
- M1-M5
- M3 is involved with the lungs
284
What is the involvement of the M3 receptors with the airways?
- ACh binds to the M3 receptor
- Receptor couples with Gq protein
- Gq protein activates phospholipase C
- PLC catalyses the breakdown of a plasma membrane phospholipid to diacylglycerol and inositol triphosphate
- DAG acts as a second messenger and activates protein kinase C
- IP3 binds to ligand-gated Ca receptors located on the ER of the bronchial cells, which open, resulting in Ca release, stimulating bronchoconstriction
285
What happens when acetylcholine binds to a M3 receptor?
Bronchoconstriction
286
What is a adrenergic neurone?
A neurone which releases NAd
287
What are the types of alpha-adrenergic receptors?
Alpha-1 & alpha-2
288
What is the function of an alpha-1 adrenergic receptor?
Acts postsynaptically to either stimulate/inhibit the activity of different types of K channels
289
What is the function of an alpha-2 adrenergic receptor?
Acts presynaptically to inhibit noradrenaline release
290
How do beta-adrenergic receptors act?
Via stimulatory G proteins to increase cAMP in the postsynaptic cell
291
What are the three types of beta-adrenergic receptors?
- Beta-1 (heart)
- Beta-2 (lungs)
- Beta-3 (adipose)
292
What happens if adrenaline or noradrenaline binds to a beta-2-adrenoreceptor in the lungs?
Bronchodilation
293
What are the two types of receptor ligand?
Agonist and antagonist
294
What is an agonist receptor ligand?
A compound that binds to a receptor and activates it, demonstrates affinity and efficacy
295
What is an antagonist receptor ligand?
A compound that blocks the effect of an agonist by competing with a chemical messenger for its binding site - but does not activate signalling normally - thus blocking its action, has affinity but zero efficacy
296
What is affinity, in terms of receptors?
- The degree to which a particular messenger binds to its receptor
- Shown by both antagonists and agonists
297
What is efficacy, in terms of receptors?
- Describes how well a ligand activates a receptor
| - Antagonists results in no conformational change to receptor shape when it binds
298
Name two agonist receptors
- Muscarine binds to muscarinic acetyl choline receptor (mAChR)
- Nicotine binds to nicotinic acetyl choline receptor (nAChR)
299
Name a antagonist receptor
Atropine binds to muscarinic acetyl choline receptor (mAChR) - reverses effect of acetyl choline e.g. use to help people poisoned with sarine (from homeland)
300
How do beta agonists work as medication?
Want to increase bronchodilation (sympathetic)
301
How do muscarinic antagonists work as medication?
Want to decrease bronchoconstriction (parasympathetic)
302
What is the neurotransmitter, receptor and effect of the parasympathetic system in the lungs?
- Neurotransmitter = ACh
- Receptor = Muscarinic 3
- Effect = Constriction
303
What is the neurotransmitter, receptor and effect of the sympathetic system in the lungs?
- Neurotransmitter = NAd which acts on adrenal glands to release adrenaline
- Receptor = Beta-2-adrenoreceptor
- Effect = Dilation
304
What is the non-immune host mechanisms of lung defence?
Barrier function, leucocyte recruitment, cytokine and growth factors
305
What is the structure of the epithelium of the lungs?
- Tissue composed of cells that line the cavities and surfaces of structures throughout the body
- Lies on top of connective tissue - the two layers are separated by a basement membrane
306
What is respiratory epithelium?
Ciliated pseudostratified columnar epithelium
307
What are the functions of the respiratory epithelium?
- Serve to moisten and protect the airways
- Functions as a barrier to potential pathogens and foreign particles
- Prevents infection and tissue injury by action of the mucociliary escalator
308
What doe the skin, salivary and lacrimal glands secrete?
- Antimicrobial chemicals e.g.
- Antibodies
- Lysozymes
- Lactoferrin
309
What is a lysozyme?
An enzyme which destroys bacterial cell walls
310
What is lactoferrin?
An iron-binding protein which prevents bacteria from obtaining the iron they require to function properly
311
Where is the respiratory tract secretes mucus?
The respiratory epithelium and upper gastrointestinal tract
312
What is significant about the mucus secreted by the respiratory tract?
- Contains antibodies
- It is also very sticky - particles adhere to it and are reverted from entering the blood
- They are either swept by ciliary action up to the pharynx and then swallowed, or are phagocytosed by macrophages
313
Name 3 other chemical barriers produced by respiratory epithelia
- Anti-fungal peptides
- Anti-microbial peptides
- Huge amount of non-pathogenic bacterial flora in the deep of the lungs - helps keep the immune system primed for pathogens
314
Name the 2 physical defence mechanisms
Coughing and mucus
315
Is a cough voluntary or reflexively?
Either
316
Where are the receptors for the cough reflex?
In the larynx, trachea and bronchi
317
What causes a deep inspiration for the cough reflex?
The receptors stimulating the medullary inspiratory neurones
318
What happens during a cough?
- The epiglottis is closed
- The vocal cords shut tightly to entrap air within the lung
- The abdominal muscles contract forcefully, pushing against the diaphragm
- The internal intercostal muscles also contract forcefully
- Pressure in the lungs rise
- Positive intrathoracic pressure causes narrowing of the trachea
- Vocal cords and epiglottis suddenly open widely
319
What is the purpose of coughing as a defence mechanism?
Particles & secretions are moved from smaller to larger airways, and aspiration of materials into the lungs is also prevented
320
What is airway mucus?
A viscoelastic gel containing water, carbohydrate, proteins and lipids
321
What is airway mucus a secretory product of?
The goblet cells of the airway surface epithelium and submucosal glands
322
What is the protective role of airway mucus?
It protects the epithelium from foreign material and fluid loss
323
How is airway mucus transported from the lower respiratory tract to the pharynx?
By airflow and the mucociliary clearance/escalator
324
How does the mucociliary escalator bring up mucus?
Does this continuously by cilia beating in directional waves up the airway
325
How does airway mucus protect the epithelium and what does it consist of?
- By being in physical contact with it
| - Has a superficial gel/mucous layer and a liquid/periciliary (surfactant) fluid layer which bathes the epithelial cells
326
How can the epithelium repair itself after injury?
Due to the fact that epithelium exhibits a level of functional plasticity
327
What are neutrophils & macrophages?
Phagocytes, some are antigen presenting cells
328
What are lymphocytes?
They make antibodies, kill diseased cells and decide what sort of antibodies to make
329
What is humoural immunity?
- Things that are in the blood/plasma NOT cells
- Immunoglobulins
- Complement (formation of the membrane attack complex)
- Surfactant proteins
- Cytokines
330
What are cytokines?
Proteins which allow leukocytes and tissue cells to talk to each other
331
What is innate immunity?
- Immediate
- Doesn't require prior exposure to recognise that something is wrong
- Mainly involves phagocytosis of bacteria and rapid responses to viruses
332
What is adaptive immunity?
- Hypersensitivity is more prevalent in adaptive
| - The formation of immunological memory
333
What is the purpose of inflammation?
The local response to infection or injury
334
What are the main functions of innate immunity?
- Destroy or inactivate foreign invaders
| - Set the stage for tissue repair
335
What are the key mediators in innate immunity?
Cells that function as phagocytes - the most important of which being neutrophils, macrophages and dendritic cells
336
What are the basic stages of innate immunity?
- Bacteria are introduced to a wound
- Chemical mediators cause vasodilation & capillary permeability; chemoattractants recruit neutrophils to the area
- Diapedesis (passage of leukocytes out of the blood and into the surrounding tissue) results in neutrophils entering tissue where they engulf and phagocytose bacteria
- Capillaries return to normal as neutrophils continue to clear the infection
337
How is acute inflammation initiated in the lung?
- Initiated by the tissues, typically by specialist tissue resident macrophages including:
- Kupffer cells
- Alveolar macrophages
338
How do macrophages respond to pathogens or tissue?
By recognising:
- Pathogen associated molecular patterns (PAMPs)
- Damage associated molecular patterns (DAMPs)
339
How do PAMPs and DAMPs work?
They recognise new pathogens that haven't been seen before by using patterns recognition receptors which are part of innate immunity which recognise common antigens on bacteria
340
Where are Toll-like receptors expressed?
In the plasma & endosomalw membranes of macrophages and dendritic cells amongst others
341
How do Toll-like receptors work?
- The proteins recognise and bind to PAMPs
- When binding of a TLR occurs on the plasma membrane of a macrophage, there is stimulation of the activity of the immune cells involved in the innate immune response (e.g. neutrophils)
342
What are the functions of alveolar macrophages?
- Phagocytosis
- Secrete cytokines
- Activation and differentiation of helper T cells
343
What is the origin of alveolar macrophages?
- Arise from monocytes (enter tissues and transform into macrophages - produced in the bone marrow)
- Long lived
344
What is the role of monocytes linked to phagocytes?
High phagocytic capacity - bacteria and apoptotic cells
345
What is the role of monocytes relating to ATP?
Intermediate ATP production
346
Which cells of the respiratory system has a high susceptibility to apoptosis?
Monocytes
347
What is the role of tissue macrophage linked to phagocytes?
High-intermediate phagocytic capacity
348
What is the role of tissue macrophages relating to ATP?
High ATP generation
349
Which cells of the respiratory system has a low susceptibility to apoptosis?
Tissue macrophage
350
What are the functions of the alveolar macrophage?
- Resident phagocyte of the lungs
351
What part of the respiratory system co-ordinates the inflammatory response?
Alveolar macrophages - cytokine production
352
What induces and clear apoptotic cells of the alveolar macrophage?
Alveolar macrophages
353
What is the level of the response of the alveolar macrophage?
- Meant to destroy bacteria swiftly and with little help
| - Macrophage can illicit a huge response by calling neutrophils - causing pneumonia
354
What percentage of white blood cells are neutrophils?
70%
355
How many neutrophils can be made per minute?
80 million
356
Where are neutrophils produced?
Bone marrow
357
What is the purpose of the granules in neutrophils?
Released to help combat infection through degranulation
358
What do primary granules of the neutrophils contain?
- Enzymes to carry out anti-microbial activity
- Elastase (breaks down elastin in lung - enables neutrophil to migrate through lung)
- Anti-bacterial proteins
359
What is the function of elastase?
Breaks down elastin in the lung, so enables neutrophil to migrate through lung
360
What do secondary granules of the neutrophils contain?
- Receptors
- Lysozymes
- Collagenase
361
What is the function of lysozyme?
Enzyme that breaks down bacterial cell walls
362
What is the function of collagenase?
Enzyme which breaks down collagen, allows neutrophils to penetrate hard to reach mollagenised areas
363
How do neutrophils recognise the threat at hand?
- Recognises bacterial structure
- Has receptors to detect host mediators
- Recognises host opsonins
364
What is a host opsonin?
Any substance that binds a microbe to a phagocyte and promotes phagocytosis
365
What is the process of the activation of neutrophils?
- They are often in the switched off state
- Activated via stimulus response coupling
- Signal transduction pathways involving calcium, protein kinases, phospholipase and G proteins
366
What is the process of adhesion of neutrophils?
- Becomes loosely tethered to endothelial cells of blood vessels. This exposes the neutrophil to chemoattractants being released in the area
- These act on the neutrophil to induce the rapid appearance interns, which bind tightly to their matching molecules on the surface of endothelial cells - meaning tight binding
367
What is the process of migration/chemotaxis of neutrophils?
- A narrow projection is placed between two endothelial cells, where the neutrophil squeezes through and gets into the interstitial fluid
- Neutrophils follow a chemotactic gradient to the area of the pathogens
368
What is the process of phagocytosis of neutrophils?
- There is contact between the phagocyte and microbe. The major trigger in this is the interaction of phagocyte receptors
- Chemical factors can bind the phagocyte tightly to the microbe and enhances phagocytosis
- When the phagocyte engulfs the microbe it is trapped in a internal sac called a phagosome isolating the microbe within the neutrophil
369
What is the process of bacterial killing of neutrophils?
- The phagosome membrane then makes contact with the lysosome to make a phagolysosome
- The microbe is broke down
370
What is the general process of necrosis?
- Cells swell, then lyse, so other enzymes are released
- Can cause damage to surrounding tissues
- Results in inflammation and phagocytosis of necroses cell
371
What is the general process of apoptosis?
- More controlled
- Cell is turned off and packaged to the be phagocytose by neutrophils
- No surrounding tissue damage
372
What system does initial responses to pathogens use?
Innate (e.g. phagocytosis)
373
What system does later responses to pathogens use?
Adaptive
374
What are the cells of the adaptive immune system?
- T-cells
- B-cells
- Macrophages
375
What are T cells?
- Type of lymphocyte
| - Involved in cell-mediated immunity and the direct killing of cells
376
Where are T cells made?
Made in bone marrow, mature in thymus
377
What is the function of the cytotoxic T cell?
They travel to the location of their target, bind to them via antigens on these target and directly kill by secreted chemicals
378
What is the function of T helper cells?
Assist in the activation and function of B cells, macrophages and cytotoxic T cells
379
What is the function of B cells?
- Type of lymphocyte
- Involved in antibody production (when activated it causes them to differentiate into plasma cells which secrete antibodies)
380
Where are B cells made?
Made in bone marrow, stored in secondary lymphoid organs
381
What are the 5 types of antibody?
IgA, IgD, IgE, IgG and IgM
382
Which antibody is made to things we are allergic to?
IgE
383
What is the most abundant type of antibody?
IgG
384
Which antibody is made at the beginning of infection?
IgM
385
What are the functions of the adaptive immune response?
- The recognition of specific non-self antigens
- Generation of responses tailored to eliminate specific pathogens or pathogen- infected cells
- Development of immunological memory
386
What is hypersensitivity?
The over-reaction by the immune system to things you don't need to react to
387
What is a type I sensitivity reaction?
- Allergic, acute
- Examples - acute anaphylaxis, hay fever
- Immediate & acute
388
What is a type II sensitivity reaction?
- IgG bound to cell surface antigens/IgM
- Examples - Transfusion reactions, autoimmune disease
- Fairly quick
389
What is a type III sensitivity reaction?
- Immune complexes, activation of complement/IgG
| - Examples - SLE, post-strep GN
390
What is a type IV sensitivity reaction?
- T cell mediated delayed type hypersensitivity (DTH)
| - Examples - TB & contact dermatitis
391
What happens in anaphylaxis?
- Severe hypotension
- Vasodilation
- Bronchoconstriction (causing mucous hypersecretion)
392
What does histamine do in a type I sensitivity reaction?
They initiate a local inflammatory response
393
What are the structural and functional changes with ageing in the lung?
- Delayed response to hypercapnia and hypoxia - increased vulnerability to ventilatory failure
- FEV and FVC decreases, so FEV1/FVC decreases, so reading may come across as obstructive
394
What is a cause of impaired gas exchange?
Due to changes in the shape of the thorax
395
What happens to costal cartilage in impaired gas exchange?
Becomes stiffer - harder to breathe
396
What happens to respiratory muscle in impaired gas exchange?
Decreases in mass - less effective
397
What happens to type IIA muscle fibres in impaired gas exchange?
Reduce - thus get more tired while breathing = breathe less/less efficiently
398
What happens to muscle fibres in impaired gas exchange?
Denervation - less contraction, thus less potent inspiration
399
What happens to elastic recoil in impaired gas exchange?
It is lost
400
What happens to elastin fibres in impaired gas exchange?
In the alveoli and respiratory bronchioles they degenerate and rupture
401
What happens to V/Q mismatch in impaired gas exchange?
Increases
402
What happens to the alveolar surface area in impaired gas exchange?
Reduces
403
What happens to lung capillary and blood flow in impaired gas exchange?
Reduces
404
What happens to oxygen saturation with normal ageing?
Declines. Not important until times of demand
405
What happens to the immune system function in impaired gas exchange and what happens?
- Decreases
- Glandular epithelia cells decrease thus less protective mucus
- Decrease sputum clearance
- Less effective mucociliary system
406
Define PiO2
Pressure of inspired oxygen (can change)
407
Define FiO2
Fraction of inspired oxygen (0.21 - never changes)
408
What is the Pigas equation?
Pigas = Patm x Figas
409
What is extremely high altitude?
18,000 feet
410
What is PaCO2 directly proportional to?
1/alveolar ventilation
411
How can PAO2 be calculated?
- PAO2 = PiO2 - (PaCO2/R)
- R = respiratory quotient (CO2 produced/O2 consumed)
- A = alveolar
- a = arterial
412
What is respiratory quotient and what is it's normal value?
- CO2 produced/O2 consumed
| - 0.8 with normal diet
413
How can PaO2 be calculated?
- PaO2 = PAO2 - (A-aDO2)
- A = alveolar
- a = arterial
- A-aD = arterial-alveolar difference (usually 1kPa due to ventilation-perfusion mismatch)
414
What is the normal blood PaO2 at sea level?
10.5 - 13.5 kPa
415
What is the normal blood PaCO2 at sea level?
4.5 - 6.0 kPa
416
What is the normal blood pH at sea level?
7.36 - 7.44
417
What happens to pressure as altitude rises?
Pressure decreases (not a linear relationship)
418
Does the value for FiO2 change at different altitudes?
It remains constant at around 0.21
419
What happens to PiO2 with altitude?
Falls with altitude
420
What is the normal response to altitude on the lungs?
- Hypoxia leads to hyperventilation
- Increased minute ventilation
- Lowers PaCO2
- Alkalosis initially & tachycardia
421
How can respiratory alkalosis be compensated for?
By renal bicarbonate excretion
422
When diving, how far does it take to drop one atmosphere?
Every 10 meters, it drops one atmosphere
423
What is Boyle's law?
- At a constant temperature, the absolute pressure of a fixed amount of gas is inversely proportional to its volume
- P1V1 =P2V2
424
What is Henry's law and how does it relate to descent?
- The amount of gas dissolved in a liquid at a given temperature is directly proportional to the partial pressure of the gas
- Thus proportionally more gas dissolves in the tissues at depth
425
What may happen in relation to the lungs with free diving?
- Aponea
- Bradycardia
- Peripheral vasoconstriction
426
What is the purpose of the lungs in the foetus?
No purpose
427
What is the respiratory tract derived from in embryo?
The foregut (anterior out pouching) endoderm and associated mesoderm
428
Which part of the respiratory tract is derived from the endoderm?
Epithelial lining of trachea, larynx, bronchi and alveoli
429
Which part of the respiratory tract is derived from the splanchnic mesoderm?
Cartilages, muscle, connective tissue of tract & visceral pleura
430
When do the lung buds develop in embryo?
- During the 4th week
| - Initially appears as the respiratory diverticulum
431
What is the respiratory diverticulum?
A ventral outgrowth of foregut endoderm
432
When do the left and right bronchi develop in embryo?
During week 5 of development
433
When to terminal bronchioles give way to terminal sacs in embryo?
Week 16
434
When are alveolar sac, type I & II pneumocytes developed in embryo?
Week 24+
435
What happens in weeks 5-17 in embryo (respiratory)?
- Major airways defined
- Nests of angiogenesis
- Smaller airways down to respiratory bronchioles
436
What happens in weeks 16-24 in embryo (resp)?
- Terminal bronchioles
| - Alveolar ducts
437
What happens in weeks 24-40 in embryo (resp)?
Alveolar budding, thinning ad complexification
438
How does the foetal circulation work?
- Shunting of blood from right to left
| - Higher vascular resistance in the lungs meaning higher pressure in right side (supplies lungs)
439
Where does right-to-left shunting happen?
Through the foramen ovale
440
What is the main purpose of the systemic circulation?
To deliver oxygen to hypoxic tissue
441
Name 3 vasodilators
- Hypoxia
- Acidosis
- Carbon dioxide
442
Why do arteries dilate in hypoxia?
So more oxygen can be provided to tissues
443
Why is there vasoconstriction when there are high levels of oxygen?
As not as much oxygen is required
444
In systemic circulation, is oxygen a vasodilator or vasoconstrictor?
Vasoconstrictor
445
What is the purpose of pulmonary circulation?
Pick-up oxygen from oxygenated lung
446
What are the vasoconstrictors in pulmonary circulation and why?
- Hypoxia
- Acidosis
- Blood will be shunted away to alveoli with better ventilation
447
In pulmonary circulation, is oxygen a vasodilator or vasoconstrictor and why?
- Vasodilator
| - Dilation will mean more oxygen can be picked up
448
What is the process of birth and the lungs?
- Fluid in lungs is squeezed out by birth process
- Adrenaline released due to stress = increased surfactant
- Air inhaled
- Oxygen vasodilators pulmonary arteries
- Umbilical arteries and ductus arteriosus constrict becoming the medial umbilical ligaments & ligament arteriosum
449
When does the production of surfactant in the lungs begin?
- Produced by type 2 pneumocytes from 34 weeks gestation
| - Production rapidly increases 2 weeks prior to birth
450
What are the functions of the respiratory system?
- Filtration, humidification & warming
- Olfaction and tased
- Gas transport/exchange
- Protection against infection
- Speech
451
Where does the respiratory epithelium line?
The tubular portions of the respiratory tract
452
What is respiratory epithelium?
Pseudostratified ciliated columnar epithelial cells interspersed with goblet cells
453
What are the 4 main functions of the nose?
- Filtration
- Humidification
- Warming
- Olfaction
454
What is the epithelium of the nose?
- Keratinising & non-keratinising squamous epithelium
| - Respiratory epithelium
455
What is the structure of the lamina of the nose?
- Richly vascular
- Contains seromucinous glands
- Vascular so it can rapidly warm and humidify air
456
Where does olfaction happen in the nose?
Roof of nasal cavity, extending down septum and lateral wall
457
What is the structure of the epithelium of the olfactory portion of the nose?
- Pseudostratified columnar epithelium of olfactory cells
- Serous glands of Bowman
- Richly innervated lamina propria
458
What are the main functions of the nasopharynx?
- Gas transport
- Humidification
- Warming
- Olfaction
459
What is the epithelium of the nasopharynx?
Respiratory epithelium
460
Give 3 functions of the nasal sinuses
- Lower the weight of the skull
- Add resonance to voice
- Humidify & warm inspired air
461
What is the epithelium of the nasal sinuses?
Respiratory epithelium
462
What is the structure of the larynx?
- A cartilaginous box
| - Loose fibrocollagenous storm with seromucinous glands
463
What is the function of the larynx?
Voice production
464
What is the epithelium of the larynx?
Respiratory epithelium
465
What is the function of the vocal chords?
Voice production
466
What is the structure of the vocal cords?
- Stratified squamous epithelium overlying loose irregular fibrous tissue (Reinke's space)
- Almost no lymphatics
467
What is the function of the trachea?
Conducts air to and from the lungs
468
What is the epithelium of the trachea?
Respiratory epithelium
469
What is posterior to the trachea?
The tracheal muscle
470
What are the glands in the trachea?
Seromucinous glands in submucosa
471
What is the general structure of the trachea in terms of cartilage?
C-shaped cartilaginous rings
472
What is the most numerous cell in the terminal bronchioles?
Clara cells
473
What is the function of Clara cells?
Secretory
474
What is the first part of the distal respiratory tract?
Respiratory bronchioles
475
What is the function of the respiratory bronchioles?
Gas exchange as well as transport
476
What do the respiratory bronchioles link?
The terminal bronchioles and alveolar ducts
477
What is the epithelial structure of the respiratory bronchioles?
Cuboidal ciliated epithelium
478
What is the structure of the smooth muscle of the respiratory bronchioles?
Spirally-arranged (also no cartilage)
479
How many alveoli are present per lung?
150-400 million
480
What is the structure of type 1 pneumocytes?
Flattened cells, flattened nucleus, few organelles - main gas exchangers
481
What is the structure of type 2 pneumocytes?
Rounded cells, round nucleus, rich in mitochondria, smooth and rough ER
482
Which cells produce surfactant in the lungs?
Type 2 pneumocytes
483
What is the structure of alveolar macrophages?
Luminal cells, also present in the interstitium
484
What is the function of the alveolar macrophages?
- Phagocytose particulates including dust and bacteria
| - Enter lymphatics or leave via mucociliary escalator
485
What is the structure of the alveoli blood-air barrier?
- 1 pneumocyte thick
- Fused basement membrane of pneumocyte and capillary
- Vascular endothelial cell
486
What is the structure of the visceral pleura?
- Flat mesothelial cells
- Loose fibrocollagenous tissue
- Irregular external elastic layer
- Interstitial fibrocollagenous layer
- Irregular internal elastic layer
