Respiration principles Flashcards
What are the steps of respiration (4)
ventilation
Gas exchange between alveoli and blood
Gas transport in blood
Gas exchange at a tissue level
What type of processes are inspiration and expiration
Inspiration is an active process
Expiration is a passive process (except in exercise)
What occurs to the body during inspiration (2)
respiratory muscles contract
Chest wall and lungs are stretched
What is the mechanism of inspiration (2)
increase in the size of the lungs decreases intracellular-alveolar pressure
Air enters lungs down its pressure gradient until intracellular-alveolar pressure equals atmospheric pressure
What occurs during expiration (3)
Muscles of inspiration relax
Volume of thoracic cavity is reduced
Volume of lungs is reduced
what enables chest wall and stretched lungs to return to their pre-inspiration size
recoil due to elastic properties
What effect does recoil of the lungs have (2)
intra-alveolar pressure rises
Air leave as the lungs down its pressure gradient until intracellular-alveolar pressure equals atmospheric pressure
What limits the expansion of alveoli
their lining of a fluid that creates surface tension
What counters the limiting effect of the fluid lining alveoli
Surfactant which has detergent-like properties
Stabilises inflation of alveoli
What secretes surfactant for alveoli
type II pneumocytes
Describe the plural seal (2)
a seal created by fluid in space between visceral and partial pleura
Keeps the lungs against the chest wall without physical attachment
Describe the pressure of the pleural space (2)
negative
Because elastic recoil of the lungs pulls visceral pleura inwards and the chest wall pulls parietal pleura outwards
What forces move the lungs and chest wall (3)
Compliance
Elastance
Pressure gradients
What resistances do the lungs and chest walls overcome (3)
air-liquid surface tension
Elastic properties of alveolar walls
Airway radius
What is elastic recoil pressure
A measure of elastance
What determines frictional resistance of airways
Air flow
What are pressure flow characteristics determined by (3)
Airway resistance
Parenchymal resistance
Chest wall chest resistance
What effect does parasympathetic stimulation have on the respiratory tree
Bronchoconstriction
What effect does sympathetic stimulation have on the respiratory tree
bronchodilation
What muscles are involved in tidal inspiration (2)
diaphragm
External intercostals
What are the accessory muscles of active inspiration (3)
sternocleidomastoid
Scalenes
Pectoral muscles
What muscles are involved in active expiration (2)
abdominal muscles
Internal intercostal muscles
Tidal volume definition
volume of air entering/leaving lungs in a single breath
Inspiration reserve volume
extra volume of air that can be maximally inspired over the typical resting tidal volume
Expiratory reserve volume
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after resting tidal volume
Residual volume
minimum volume of air remains in lungs after maximal expiration
Which lung volume cannot be measured directly with spirometers
Residual volume
Inspiratory capacity
maximum volume of air that can be inspired at the end of normal tidal expiration
Functional residual capacity
volume of air in the lungs at the end of normal, passive expiration
Vital capacity
maximum volume of air that can be moved out during a single breath following a maximal inspiration
Total lung capacity
total volume of air lungs can hold
What can be determined from a volume-time curve (2)
Forced vital capacity
Forced expiratory volume in one second
What is the expected FEV1/FVC ratio
Greater than or equal to 75%
What are the types of lung diseases (2)
obstructive
Restrictive
Describe obstructive lung disease
when there is reduced expiratory flow and air trapping
Describe restrictive lung disease
when the lungs have a reduced functional volume
What increases in cases of obstructive lung disease (3)
total lung capacity
Residual volume
Functional residual capacity
What decreases in cases of restrictive lung disease (3)
Total lung capacity
Residual volume
Functional residual volume
What does anatomical dead space refer to
How some inspired air remains within airways where it is not available for gas exchange
Which is lower: alveolar/pulmonary ventilation and why
Alveolar
Due to presence of anatomical dead space
What is alveolar ventilation (2)
volume of air exchanged between atmosphere and alveoli per minute
Represents new air available for gas exchange with blood
What is atmospheric pressure
Pressure exerted by weight of air above earth in the atmosphere
What law dictates the mechanism of inspiration and expiration
Boyle’s law
What is partial pressure
pressure exerted by a dissolved gas in a liquid
In atmospheric air, what are the partial pressures of oxygen and carbon dioxide
O2 - 21.1 kPa
CO2 - 0.03 kPa
What happens when inspired gases come into contact with body fluid (2)
gas molecules enter water and dissolve in liquid
Water molecules evaporate to enter air and exert a vapour pressure
what requirement is there is a gas reacts with a component of liquid
the reaction must complete before equilibrium is reached and partial pressure is established
Describe interaction between oxygen and blood (4)
when oxygen enters plasma it dissolves
The dissolved oxygen enters RBC and binds to haemoglobin
Until haemoglobin is fully saturated
Once it is saturated, oxygen continues to dissolve until equilibrium is reached
What is pO2 a measure of
dissolved oxygen in blood
As dissolved oxygen leaves the blood and diffuses into tissues, what happens
it is replaced by the oxygen bound to haemoglobin which in turn also diffuses into tissues
What are the partial pressures of oxygen and carbon dioxide in alveolar air
O2 - 13.3 kPa
CO2 - 5.3 kPa
Describe what happens in alveolar air (3)
Inhaled air mixes with residual volume
Oxygen diffuses across alveolar wall
Carbon dioxide enters the alveoli
What factors affect the rate of gas diffusion (3)
partial pressure gradient across membrane
Surface area available
Thickness (distance to travel)
What can alter the distance molecules must diffuse (2)
Increases due to oedema fluid in interstitial spaces and alveoli
Increases due to increased thickeners of alveolar capillary membrane (lung fibrosis)
Which is more soluble: carbon dioxide or oxygen
carbon dioxide
Which has a greater molecular weight: carbon dioxide or oxygen
carbon dioxide
What compensates for slower diffusion of oxygen (compared to carbon dioxide)
larger difference in partial pressures
Why is oxygen exchange more impaired (than CO2) in a diseased lung
Due to slower oxygen diffusion rate
Wha are the components of the diffusion barrier (6)
Fluid film lining of alveoli
Epithelial cells of alveoli
Interstitial space
Endothelial cells of capillaries
Plasma
RBC membrane
What does haemoglobin consist of
2 alpha subunits
2 beta subunits
Describe T state of haemoglobin (2)
low affinity for oxygen
Occurs when pO2 is low
Describe R state of haemoglobin (1)
high affinity for oxygen
At what pO2 is haemoglobin half saturated
3.5-4 kPa
At what pO2 is haemoglobin saturated
9-10 kPa
Describe levels in a patient with anaemia btu normally functioning lungs (2)
normal pO2
Lower oxygen content
What does tissue pO2 depend on
Metabolic activity of the tissue
What does tissue pO2 determine
how much oxygen will dissociated from haemoglobin - the lower the pO2, the more oxygen will dissociate
Why must tissue pO2 be sufficiently high
To drive diffusion of oxygen to cells
In what situations can tissue pO2 fall lower without negatively impacting oxygen diffusion (2)
in tissues with high capillary density
Because this means that oxygen does not have as far to diffuse
What does the Bohr shift refer to (2)
the relationship between pH and haemoglobin’s affinity for oxygen
Acidic conditions shift the dissociation curve to the right and promote the T state of haemoglbin
Describe pH in relation to metabolic activity (2)
pH is lower in metabolically active tissues
Meaning that more oxygen is given up
Describe temperature in relation to metabolic activity (2)
Temperature is higher in metabolically active tissues
This means that more oxygen is given up
When does maximum unloading of oxygen occur (2)
when tissue pO2 can fall to a low level
When increased metabolic activity leads to a more acidic environment with a higher temperature
Describe effect of extreme exercise in relation to oxygen (3)
Metabolism can increase 10x
Cardiac output can only increase 5x
This improves oxygen extraction by tissues
Which cells contain 2,3-biphosphoglycerate
Red blood cells
In what situations do levels of 2,3-biphosphoglycerate increase (2)
Anaemia
High altitude
What is the effect of increased 2,3-biphosphoglycerate (2)
shifts haemoglobin dissociation curve to the right
Allows more oxygen to be given up to tissues
Describe carbon monoxide poisoning (3)
CO reacts with haemoglobin to form COHb
This increases the unaffected subunits’ affinity for oxygen
Oxygen wont be given up at tissues
What does hypoxaemia refer to
low pO2 in arterial blood
Why is hypoxaemia a problem (2)
when pO2 levels are too low, not all haemoglobin will be saturated
So not enough oxygen will be present in the blood
What does hypoxia refer to
inadequate oxygen levels in the body/tissues
What can cause peripheral hypoxia
peripheral vasoconstriction
What are examples of issues where tissues use oxygen faster than it is delivered (2)
peripheral arterial disease
Raynaud’s
Describe cyanosis
discolouration due to unsaturated haemoglobin
Deoxygenated haemoglobin is less red than oxygenated haemoglobin
What does pulse oximetry detect (2)
Levels of haemoglobin saturation
Difference in absorption of light between oxygenated and deoxygenated haemoglobin
What does pulse oximetry NOT detect
how much haemoglobin is present
Which is more abundant in arterial blood: CO2 or O2
CO2
What are the roles of CO2 (2)
Metabolic waste product
Controlling blood pH
What is the pH range of arterial blood
7.35-7.45
Describe what happens when carbon dioxide comes into contact with liquid (2)
CO2 dissolves in water
Dissolved CO2 reacts with the water in plasma RBC
What is formed when dissolved CO2 reacts with water
carbonic acid
Describe action of carbonic acid
it rapidly dissociates to hydrogen ions and hydrogen carbonate ions
What does pH of plasma depend on (2)
how much CO2 reacts to form hydrogen ions
And so on [dissolved CO2] and [hydrogen carbonate]
What does quantity of CO2 dissolved depend on
Partial pressure of CO2
(Higher pCO2, lower plasma pH)
What controls pCO2 in alveoli
rate of breathing
Which cation is associated with hydrogen carbonate
Na+
Why is pH of plasma alkaline
the high concentration of hydrogen carbonate prevents almost all dissolved CO2 from reacting (to form hydrogen ions)
What ration determines pH of arterial blood
[hydrogen carbonate] to pCO2
Describe hydrogen carbonate production in red blood cells (3)
Catalysed by carbonic ahydrase
Proceeds in a forward direction as products are removed
Hydrogen ions bind to haemoglobin
how is hydrogen carbonate removed in the production reaction in red blood cells (2)
Chloride-bicarbonate exchange transports the hydrogen carbonate out of RBC
This means that the plasma concentration of hydrogen carbonate is higher
What controls the quantity of hydrogen carbonate
kidneys (by varying excretion)
Function of hydrogen carbonate
Buffer - acids react with hydrogen carbonate to form carbon dioxide which can be expelled via breathing
How does pCO2 of arterial and venous blood compare and why
pCO2 is higher in venous blood
Because this blood is sourced form metabolically active tissues (more CO2 dissolved)
What does the level of buffering of hydrogen ions by haemoglobin depend on
oxygenation - more oxygen bound to haemoglobin means less hydrogen ions bound to haemoglbin
Why is there a slight change in plasma pH in venous circulation
[hydrogen carbonate] and pCO2 are increased
What happens when venous blood arrives at the lungs (4)
haemoglobin picks up oxygen - goes towards R state
Haemoglobin therefore gives up extra hydrogen ions
Hydrogen ions given up then react with hydrogen carbonate, producing CO2
CO2 is expired
Which part of haemoglobin can CO2 bind to
Amine groups of globin
Why are more carbamino compounds formed at tissues (2)
pCO2 is higher
Unloading of oxygen facilitates CO2 binding to haemoglobin
What happens to the CO2 bound to haemoglobin
it is given up at lungs
In what three forms can CO2 be transported
hydrogen carbonate
Carbamino compounds
Dissolved
What are the two steps of coughing
Sensory receptors are stimulated in the mucosa
The central nervous system responds
During coughing, in what structures is the mucosa stimulated (4)
oropharynx
Laryngopharynx
Larynx
Respiratory tree
How does the central nervous system respond to stimulation of sensory receptors in the mucosa (5)
Deep inspiration
Adduction of vocal chords
Contraction of anterolateral abdominal wall muscles
Abduction of vocal cords
Tensing of soft palate
Which muscles does deep inspiration involve (3)
diaphragm
Intercostal
Accessory muscles
What is the result of adduction of the vocal cords
the rima glottis closes
What is the effect of contraction of the anterolateral abdominal wall muscles (3)
builds up intracellular-abdominal pressure
Diaphragm is pushed superiorly
Pressure build up in chest and respiratory tree
What is the result of abduction of the vocal cords
rima glottidis opens
What is the effect of the soft palate tensing and elevation (2)
closes off entrance to nasopharynx
Directs stream of air through oral cavity
What are the carotid sheaths
protective tubes of cervical deep fascia found near the bones at the base of the skull
What do the carotid sheaths contain
vagus nerve
Internal carotid artery
Common carotid artery
Internal jugular vein
What supplies the d
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