Respiratory Physiology Flashcards
What are the 4 functions of the respiratory system?
Gas exchange
Acid base balance
Protection from infection
Communication via speech
What gas is added from the air to the blood?
O2
What gas is removed from the blood into the air?
CO2
What is the respiratory system responsible for?
Acquiring oxygen
Removing carbon dioxide
What system does the respiratory system need?
The cardiovascular system
Where does the cardiovascular system transport oxygen?
To tissues
Where does the cardiovascular system transport carbon dioxide?
Away from tissues
What does cellular respiration need?
Oxygen
What is the waste product of cellular respiration?
Carbon dioxide
Where does the pulmonary artery travel?
Away from the heart
Where does the pulmonary vein travel?
Towards the heart
What is the function of pulmonary circulation?
Deliver CO2 to lungs and pick up O2
What is the function of systemic circulation?
Deliver O2 to cells
Remove CO2 from cells
In the steady state what is the relationship between the gases exchanged in the lungs and tissue?
The net volume of oxygen and carbon dioxide exchanged in the lungs per unit of time is equal to the net volume exchanged in the tissues
What does gas exchange being equal in the lungs and tissues prevent?
The build up of gas in the circulation
What is the main organ of the respiratory system?
Lungs
What is a common name for the larynx?
Voice box
Where does air enter the body?
Through the nose
How many trachea are there?
1
How many bronchus are there?
2
What is the epiglottis?
Small flap of tissue that folds over the trachea preventing food from entering the air pipe when you swallow
What does the upper respiratory system compose of?
Mouth
Nasal cavity
Pharynx
Larynx (voice box)
What does the lower respiratory system compose of?
Trachea
Bronchi
Lungs
How is the patency of airways maintained?
By C shaped rings of cartilage
Where can gas exchange occur?
Alveoli
Systemic Capillaries
What organ lying inferior to the right lung causes is to be shorter and broader?
The liver
What are the 2 fissures of the right lung?
Horizontal fissure
Oblique fissure
How many bronchi does the trachea branch into?
2
How many more times does each bronchus branch?
22
Where does the bronchus terminate?
At the alveoli
Why are the alveoli covered in capillaries?
To minimise the distance of exchange
What are the alveoli covered in?
Elastic fibres
Capillaries
Describe the walls of the alveoli?
Thin walls
Why does gas not exchange at the upper airways?
Because the walls are too thick
What is the air in the upper airways known as and why?
Anatomical dead space
Because it cannot participate in gas exchange
What features of the alveoli make it so effective for gas exchange?
Thin walls
Large surface area
What is airway diameter altered by?
Activity of bronchial smooth muscle
What is the function of mucous in the respiratory tract?
To moisten the air
To trap large and invasive particles
To provide a large surface area for cilia to work on
What cells produce mucous in the respiratory tract?
Goblet cells
What type of epithelium lines the respiratory tract?
Psuedo-stratified, ciliated, columnar
What hair like structures line the respiratory tract?
Cilia
In terms of pressure how do gases move?
From an area of high pressure to an area of low pressure
What does Boyle’s Law state?
The pressure exerted by a gas is inversely proportional to its volume
What does Daltons Law state?
The total pressure of a gas mixture is the sum of the pressure of the individual gases
What does Charles Law State?
The volume occupied by a gas is directly related to the absolute temperature
What is the lower respiratory system bound by?
Diaphragm
Spine
Ribs
How many lobes is the right lung split into?
3
How many lobes is the left lung split into?
2
What volume of pleural liquid is there in the pleural cavity?
3ml
What is function of pleural liquid?
To act as a lubricant
How many pleural membranes is each lung enclosed by?
2
What are the 2 pleural membranes?
Parietal pleura
Visceral pleura
What is inflammation of the pleural membranes known as?
Pleurisy
What is the purpose of the pleural membranes?
To anchor the lungs to the rib cage
What does the parietal pleural membrane coat?
The inner surface of the lungs
What does the visceral pleural membrane coat?
The outer surface of the lungs
Explain pneumothorax
When there is a loss of relationship of the pleural membranes
The chest wall wants to expand
The lung wants to shrink
Leads to the collapse of the lung
What muscles are used for inspiration?
Diaphragm
External intercostal muscles
Scalenes
Sternocleidomastoids
What muscles are used for expiration?
Internal intercostal
Abdominals
What is the very basic concept of breathing?
There is an increase of volume in the thoracic cavity
This decreases the pressure
Drawing air from higher pressure outside in
Is inspiration passive?
No
Is expiration passive?
Yes - AT REST
When the diaphragm contracts what happens?
It moves down
Increasing thoracic volume
What is the intra-thoracic (alveolar) pressure?
The pressure inside the thoracic cavity
Is the intra thoracic pressure + or -?
Can be either compared to the atmospheric pressure
What is the intra-pleural Pressure?
Pressure inside pleural cavity
Should the intra-pleural pressure be + or -?
Always negative (in healthy lung at least)
What is the transpulmonary pressure?
Difference between the alveolar pressure and intra-pleural pressure
What is the major determinant of airway resistance?
The radii of the airways
Are the lungs elastic?
Yes they are elastic structures
Explain expiration
The inspiratory muscles cease to contract
Allowing elastic recoil of chest wall
Lungs return to normal size
Smaller volume - greater pressure than atmospheric
Driving air out of the lungs
What do type I alveolar cells do?
Permit gas exchange
What do type II alveolar cells do?
Secrete surfactant fluid
What volume of gas does the average person breathe in and out in a breath?
500ml
What is tidal volume?
The normal inspiration and expiration of gas
What is the average volume of tidal volume?
500ml
What volume of air is the anatomical dead space?
Around 150ml
What volume is the inspiratory reserve volume?
3L
What volume is the expiratory reserve volume?
1.1L
Why is the residual volume in the lungs so crucial?
Prevents the alveoli from collapsing
What is the vital capacity?
The maximum expiration after the maximum inspiration
What is pulmonary ventilation?
Total air movement into-out of the lungs
What is alveolar ventilation?
The fresh air getting to alveoli and therefore available for gas exchange
Is the anatomical dead space air available for gas exchange?
No
Between what volumes do the lungs normally operate?
2.3L and 2.8L
How do you work out the air that reaches the alveoli?
Vol of air breathed in - 150ml of the dead space air
What affects the amount of air that reaches the alveoli? Rate or depth of breathing?
Depth
What do type I alveolar cells permit?
Gas exchange
What do type II alveolar cells secrete?
Surfactant fluid
What does surfactant fluid reduce?
Surface tension on alveolar surface
What does the compliance of the lung represent?
The stretchability of the lung
How easy it is for air to get into the lungs
Is low compliance good or bad?
Bad
What happens to the compliance of our lungs with age?
Become less compliant
Describe high compliance?
Large increase in lung volume for small decrease in ip pressure
Describe low compliance?
Small increase in lung volume for large decrease in ip pressure
What is the definition of compliance?
The change in volume relative to the change in pressure
During inspiration what needs to be overcome?
Surface tension
What does a shallower curve represent?
Lower compliance
What does a steeper curve represent?
Higher compliance
What is emphysema?
Loss of elastic tissue meaning expiration requires effort
What is fibrosis?
Inert fibrous tissue means effort of inspiration increases
As the stretchability of the lung is affected
What is the pleural membrane coating the outer surface of the lungs?
Visceral membrane
What is the pleural membrane coating the inner surface of the ribs?
Parietal membrane
Is inspiration passive?
No
Inspiration requires energy
Upon inspiration does the diaphragm ascend or descend?
Descend
Why does the diaphragm descend upon inspiration?
To increase thoracic volume
What happens with asthma?
There is an over-reactive constriction of bronchial smooth muscle.
Increasing resistance making expiration of air difficult
Why is intrapleural pressure always negative?
So it acts like a suction to keep the the lungs inflated
What is the bulk flow of air between the atmosphere and alveoli proportional to?
The difference between the atmospheric and alveolar pressures
What is the bulk flow of air between the atmosphere and alveoli inversely proportional to?
Airway resistance
Describe the end of a unforced expiration
The dimensions of the lung and thoracic cage are stable as the result of opposing elastic forces
The lungs are stretched and attempt to recoil
The chest wall is compressed and attempting to move outwards
What is the major determinant of airway resistance?
The radii of the airways
What does airway resistance determine?
How much air flows into the lungs at any given pressure
Does the increase in thoracic volume make the intrapleural pressure more negative or positive?
Negative
What is vital capacity?
Tidal volume
+ ERV
+ IRV
What is TLC?
Total lung capacity
Vital capacity + Residual volume
At birth what volume do babies lack?
Residual volume
What is hyperventilation?
When more air than normal reaches the alveoli
I.e when taking deep breaths
What is hypoventilation?
When less air than normal reaches the alveoli
I.e when taking shallow breaths
How do you measure the air to alveoli?
The tidal volume minus 150ml
What unit is pressure commonly expressed in?
mmHg
During hyper ventilation what does PO2 rise to?
120mmHg
During hyper ventilation what does PCO2 fall to?
20 mmHg
During hypo ventilation what does PO2 fall to?
30 mmHg
During hypo ventilation what does PCO2 rise to?
100mmHg
Why is the residual volume impossible to squeeze out ?
It stops the alveoli from collapsing
What is ventilation?
The movement of air in and out of the lungs (breathing)
What percentage of air in the alveoli is fresh?
70%
What cells produce surfactant?
Type II alveolar cells
What is the role of pulmonary surfactant?
To act like a detergent
Reducing the surface tension on the alveolar surface
Reducing the tendency for the alveoli to collapse
What molecular interactions of the alveoli does pulmonary surfactant interrupt?
Acts like a detergent
Interfering with the water molecule interactions on the alveoli
Why does pulmonary surfactant increase the compliance of the lungs?
As it reduces the lungs tendency to recoil
You do not have to apply extra pressure to stop the alveoli from collapsing
When does surfactant pulmonary production start?
25 weeks
Normally what is the expectation of healthy lungs regarding compliance?
Expected to be highly compliant
Is compliance related to elasticity or stretchability?
Stretchability
Describe high compliance of the lungs?
A large increase in lung volume for small decrease in ip pressure
Describe low compliance of the lungs?
A small increase in lung volume for large decrease in ip pressure
Why is low compliance bad?
Requires alot of effort for a small increase in lung volume
Does compliance increase or decrease with age?
Decrease
Where is alveolar ventilation greatest?
At the base of the lung
Where is alveolar ventilation the least?
At the apex of the lung
Why is alveolar ventilation greatest at the base of the lung?
Because the weight of the lung is pushing down on the base
Meaning the base of the lung has more potential to expand
What does a shallower curve in pressure volume graph indicate?
Lower compliance
What does a steeper curve on pressure volume graph indicate?
Higher compliance
What does low compliance indicate?
A stiff lung
What does high compliance indicated?
A pliable lung
What is obstructive lung disease?
When there is obstruction to the flow of air especially on expiration
Does obstructive lung disease particularly affect inspiration or expiration?
Expiration
What does restrictive lung disease restrict?
Lung expansion
Compliance
What happens to alveolar ventilation from the base to the apex of the lung?
It declines
What happens to compliance from the base to the apex of the lung?
It declines
Give 2 examples of obstructive lung disorders
Asthma
COPD
Chronic bronchitis
Emphysema
What is lost in emphysema?
Lung elasticity
What is chronic bronchitis?
Inflammation of the bronchi
What is infant respiratory distress syndrome?
When there is insufficient surfactant production in the babies lungs
Surfactant production normally occurs at around 23 weeks
What is oedema of the lungs?
Build up of fluid around the alveoli
Is oedema restrictive or obstructive?
Restrictive
What test is used to measure lung function?
Spirometry
Is voluntary or involuntary lung action measured with a spirometer?
Voluntary
What can be measured using spirometry?
Tidal volume
Inspiratory RV
Expiratory RV
Vital Capacity
What is FEV1?
The forced expiratory volume in 1 second
What is FVC?
The forced vital capacity
In healthy individuals what should the forced expiratory volume be?
80% of the vital capacity
Why does obstructive lung disease show a decrease in Vital capacity and FEV?
Because obstruction means they cannot blow as much air out in 1 second
Why does restrictive lung disease show an increase in %?
Because the problem was getting the air in
Meaning they can get the air out quicker as they technically do not have enough in their lungs to begin with
What are the 2 different blood supplies to the lungs?
Bronchial circulation
Pulmonary circulation
What is the bronchial circulation supplied by?
The bronchial arteries
It is the nutritive one
Explain bronchial circulation
Arises from systemic circulation
Supplies oxygenated blood to the airways smooth muscle, nerves and lung tissue
What is the pulmonary circulation used for?
Gas exchange
Is the pulmonary circulation a high or low pressure system?
Low
Is the pulmonary circulation a high or low flow system?
High
Where do the left and right pulmonary arteries arise from?
Right ventricle
Where does the pulmonary circulation return oxygenated blood to via what?
To the left atrium
Via the pulmonary vein
How does gas exchange occurs at the alveoli and tissues?
The gas moves from a high partial pressure to a low partial pressure
What is the partial pressure of O2 and CO2 in the pulmonary vein?
100mmHg for O2
40mmHg for CO2
What is the partial pressure of O2 at the tissues?
40mmHg
Explain O2 partial pressure at the tissues?
High O2 pressure in blood (100mmHg)
Low partial O2 pressure in tissues (40mmHg)
Moves down pressure gradient
Explain CO2 partial pressure at the tissues?
Low CO2 partial pressure in blood (40mmHG)
High CO2 partial pressure in tissues (46mmHg)
CO2 moves into blood down pressure gradient
What does A stand for?
Alveolar pressure
What does a stand for?
Arterial pressure
What does v stand for?
Mixed venous blood
What does PaO2 stand for?
Partial pressure of oxygen in arterial blood
What does PACO2 stand for?
Partial pressure on carbon dioxide in alveolar air
What rules does the diffusion of gas between the alveoli and blood follow?
The rules of simple diffusion
Moving down its partial pressure gradient
What is the rate of gas diffusion directly proportional to?
Partial pressure gradient
Gas solubility
Available surface area
What is the rate of gas diffusion inversely proportional to?
The thickness of the membrane
Why is the rate of O2 and CO2 diffusion similar even though O2 has a much steeper conc. gradient?
Because CO2 is much more soluble than O2 therefore diffusing faster
How thick is the alveolar membrane?
Thin as possible
Only one cell thick
Where are the alveoli directly located by and why?
Blood vessels to decrease the distance needed for gas exchange
Why does the alveolar surface have a large surface area?
To allow maximum rate of diffusion of gases
How does emphysema affect gas exchange?
Destructs alveoli
Less surface area for gas exchange
How does fibrotic lung disease affect gas exchange?
Thickened alveolar membrane slows gas exchange
How does pulmonary oedema affect gas exchange?
Fluid build up increases diffusion distance
What causes fibrosis?
Thickened walls of alveoli due to fibrosis tissue
What is shunt?
A term used to describe the passage of blood though areas of the lung that are poorly ventilated
Is inspiration controlled by smooth or skeletal muscle?
Skeletal
What nerves innervate the diaphragm?
Phrenic nerves
What controls the innervation of the muscles of breathing?
Pons, medulla
From which vertebral levels do the phrenic nerves originate?
C3,4,5
Do we have any voluntary control over our breathing?
Yes
What modulates our breathing?
Emotion
Voluntary Over ride
Chemical composition of blood
Mechano-sensory input
What is the most significant input that changes our breathing?
Chemoreceptor input
What are the two types of chemoreceptors?
Central
Peripheral
Where are central chemoreceptors located?
Medulla
Where are peripheral chemoreceptors located?
Carotid and aortic
What do central chemoreceptors reflect?
CO2
What do peripheral chemoreceptors respond to?
Plasma (H+) and PO2
What fluid bathes the central nervous system?
CSF
Cerebral spinal fluid
Can the brain and spinal cord tolerate much change to their environment (CSF)?
No
What is the blood brain barrier?
A selective barrier that protects the brain by only letting certain things cross
Is the blood brain barrier permeable to gas?
Yes
Is the blood brain barrier permeable to ions?
No
When arterial PCO2 increases what crosses the blood brain barrier?
CO2
What effect does an increase in arterial PCO2 have?
Feedback system
Increases ventilation
What effect does a decrease in arterial PCO2 have?
Feedback system
Slows ventilation rate
Below what level does haemoglobin lose a lot of saturation?
60mmHg
What happens when PO2 mmHg falls below 60mmHg?
There is a significant increase in ventilation as an attempt to get more O2 into the body
Restoring normal O2
Do alveoli have a small or large surface area?
Large
Describe the thickness of the membrane at the alveoli?
Thin membrane
What is perfusion?
The process of the body delivering blood to a capillary bed in its biological tissue
Is blood flow at the base of the lungs high or low and why?
High because arterial pressure exceeds alveolar pressure
Is vascular resistance at the base of the lung high or low?
Low
Is the blood flow at the apex of the lungs high or low?
Low because arterial pressure is less than alveolar pressure
Is vascular resistance at the apex of the lungs high or low?
Higher
If ventilation decreases what happens at the capillary bed?
PCO2 increases
PO2 decreases
Blood flowing past those alveoli does not get oxygenated
What is shunting?
Dilution of oxygenated blood from better ventilated areas
When hypoxia is detected why do blood vessels in the lungs constrict?
To allow less blood to flow to the poorly oxygenated ares
What happens to blood vessels in the rest of the body when hypoxia is detected?
They dilate
What nerves stimulate the external intercostal muscles?
Intercostal nerves
Where is emotion in the brain controlled?
Limbic system
Where does a rise in (H+) conc. come from?
CO2
If there is increased ventilation is more CO2 blown off or retained?
Blown off
If there is decreased ventilation is more CO2 blown off or retained?
Retained
Why can’t you stop yourself breathing and kill yourself?
Because after you have been knocked unconscious the innate breathing system will kick in and begin breathing again
What is ventilation reflexly inhibited by?
Increase in arterial PO2 or a decrease in arterial PCO2
When else is respiratory inhibited?
During swallowing to avoid aspiration of food or fluids
What is swallowing folloed by?
Expiration
Why is swallowing followed by expiration?
To dislodge outwards particles from the region of the glottis
What volume of O2 dissolves in 1L of water?
3ml
What does haemoglobin increase the carrying capacity of O2 to?
3ml to 200ml per litre
What cells is haemoglobin found in?
Red blood cells
What would gaseous phase gases travelling in the blood cause?
Bubbles in the blood causing fatal air embolism
What is the resting oxygen demand of tissues?
250ml/min
What % of O2 is extracted by peripheral tissues at rest?
25%
Whats the difference between HbA and HbA2?
Where delta chains replace beta chains
Whats the difference between HbA and HbF?
Where gamma chains replace beta chains
What is glycosylated Hb associated with?
Glucose
Is the glycolysation of Hb reversible?
No it is irreversible
What is the major determinant of the degree to which haemoglobin is saturated?
The partial pressure of oxygen in the arterial blood
How many subunits is haemoglobin composed of?
4
When does oxygen stop entering the plasma?
When all Hb is saturated
How much O2 does each litre of systemic arterial blood contain?
200ml
At PO2 60mmHg how saturated is haemoglobin?
90%
Do HbF and myoglobin have a higher or lower affinity for O2 than HbA?
Higher
Does foetal haemoglobin have a higher or lower affinity than the mothers haemoglobin for oxygen?
Higher affinity
Why does foetal haemoglobin have a higher affinity for O2?
So that it can acquire and pull in O2 from the mothers blood
In anaemia is there any problem with ventilation?
No
In anaemia is there any problem with diffusion?
No
Even when O2 content is low why can PaO2 be normal?
Because the haemoglobin that is present is saturated
What is anaemia?
Defined as the condition where the oxygen carrying capacity of the blood is compromised
What factors can affect haemoglobin affinity?
pH
Temperature
CO2
(DPG)
How is the affinity of haemoglobin decreased?
Decrease in pH
Increase in temperature
Increase in PCO2
How is the affinity of haemoglobin increased?
Increase in pH
Decrease in temperature
Decrease in PCO2
What does an increased affinity of haemoglobin cause?
Makes oxygen unloading more difficult
But aids the collection of oxygen in the pulmonary circulation
Is shunt perfused or ventilated?
Perfused but not ventilated
Is alveolar space ventilated or perfused?
Ventilated but not perfused
What is shunting the opposite to?
Alveolar dead space
Where does the majority of perfusion-ventilation mismatch occur?
At the apex of the lung
What should the value of perfusion-ventilation ideally be?
1
At which level does the trachea bifurcate?
T4
Which spinal nerves innervate the phrenic nerve?
C3,4,5 (keep the diaphragm alive)
What is hypoxic hypoxia?
This is when PaO2 is below normal
What is anaemic hypoxia?
This is when the lungs are in perfect working condition however the carrying capacity of )2 of the blood has been reduced
What is circulatory hypoxia?
This is when the heart cannot pump the blood to the tissues or lungs
What is metabolic hypoxia?
When oxygen delivery to the tissue does not meet increase demand by cells
Describe hypoventilation
Causes CO2 retention
Causes increase in H+ conc
Brings about respiratory acidosis
Describe hyperventilation
Blowing off more CO2,
Decreased H+ conc
Brings about respiratory alkalosis
