Respiratory Flashcards
What is the primary function of the respiratory system?
To obtain oxygen (O2) for use by the body’s cells and to eliminate carbon dioxide (CO2) produced by cells
What are the two main types of respiration?
Internal (cellular) respiration
External respiration
Draw and label a diagram showing how blood becomes oxygenated
See lecture notes
What are the non-respiratory functions of the respiratory system?
Route for water loss and heat elimination
Enhances venous return
Contributes to the maintenance of blood pH
Enables speech, singing and other vocalisation
Defends against inhaled foreign matter
Can act as a filter for blood returning to the peripheries
The nose serves as an organ of smells
What are the two key zones within external respiration?
The conducting zone:
Respiratory passageways
The respiratory zone:
The site of gaseous exchange
What structures come under the conducting zone:
The nose
The nasal cavity
The pharynx
The larynx
The trachea
The bronchi
What is the structure of the nose
Bone and cartilage
What is the function of the nose
Provides an airway for respiration
Moistens and warms entering air
Filters inspired air
Serves as a responding chamber for speech
Houses the olfactory receptors
What is the structure of the pharynx?
Funnel shaped, connects the nasal cavity and the mouth to the larynx and oesophagus
What is the function of the pharynx?
Serves as a common pathway for food and air
Commonly called the throat
What is the larynx?
Also termed the voice box because it houses the vocal cords
What is the structure of the pharynx?
Bone and cartilage
What is the function of the larynx?
To provide an open airway
Act as a witching mechanism to route air and food into the proper channels
Voice production
What is the trachea commonly termed?
The windpipe
What is the structure of the trachea?
Supported by hyaline cartilage rings
The trachea consists of three main layers:
Mucosa: contain cilia for the removal of mucus
Submucosa: connective tissue layer containing glands that produce mucus
Adventitia: outermost layer supported by ‘c’ shaped hyaline cartilage rings fixed together with trachealis muscle
What is the structure of the bronchi?
The trachea split into two, forming two distinct bronchi
These bronchi lead into the actual lung and then divide again into the secondary bronchi
The bronchi continue to sub-divide until termination, approximately 23 orders of branching
What does the respiratory zone consist of?
Bronchioles
Alveolar ducts
Alveolar sacs
What is the respiratory membrane
Walls of the alveoli are composed of squamous epithelial type I cells
The external surface of the alveoli are covered with a complex network of pulmonary capillaries
Together, the alveoli and the network of pulmonary capillaries form the respiratory membrane
Scattered amongst the type I cells are cuboidal type II cells, which secrete a fluid containing surfactant
Describe the gross anatomy of the lungs
The lungs are located in the thoracic cavity, occupying the same anatomical regions as the heart and the great blood vessels
Each lung is suspended in its own pleural cavity
The left lung consists of two lobes and is smaller than the right due to the positioning of the heart
The right lung consists of three lobes and is bigger than the left
How is blood supplied to the lungs?
Pulmonary arteries deliver deoxygenated blood to the lungs (arteries take blood away from the heart)
Pulmonary veins take oxygenated blood away from the lungs and back to the heart for systemic distribution
What is the pleura?
A thin, double layered steroids (a membrane that secretes serous fluid)
The partial pleura lines the thoracic wall and the superior aspects of the diaphragm
The visceral pleura covers the external lung surface
The pleurae produce pleural fluid, a lubricating serous secretion that fills the pleural cavity
This allows the lungs to slide freely over the thorax
Explain the difference between external and inter Earl respiration
Internal:
Internal respiration refers to the gas exchange across the respiratory membrane in the metabolising tissues
Oxygen diffuses out form the blood into tissue
Carbon dioxide diffuses into the blood from the tissue
Internal environment only
External:
External respiration refers to gaseous exchange across the respiratory membrane of the lungs
Oxygen diffuses from alveolar air into the blood
Carbon dioxide diffuses out of the blood into the alveolar air
Internal environment and external environment
Outline the non-respiratory functions of the mammalian respiratory system
See lecture notes
Describe the two main external respiratory zones
See lecture notes
Describe and name the various layers that make up the pleural cavity
See lecture notes
What is breathing?
Also known as pulmonary ventilation and occurs in two stages:
Inspiration: where air flows into the lungs
Expiration: when gases leave the lungs
The process of breathing is made possible by the presence of pressure relationships in the thoracic cavity
What is inspiration?
When air flows into the lungs
What is expiration?
When gases leave the lungs
Discuss pressure relationships in the thoracic cavity
Respiratory pressures are always described relative to atmospheric pressures
Atmospheric pressure: the pressure exerted by the air that surrounds the body
At sea level, atmospheric pressure is equal to 760mmHg
What is intrapulmonary pressure?
Pressure within the alveoli of the lungs
Intrapulmonary pressure rises and falls with the phases of breathing
However, the intrapulmonary pressure always, eventually equalises with atmospheric pressure outside of the body
What is intra-pleural pressure?
The pressure within the pleural cavity (lines the ‘gap’ between the thoracic wall and lungs)
Fluctuates with breathing phases
Intra-pleural pressure is always lower than the pressure in the alveoli (intrapulmonary pressure) hence also lower than atmospheric pressure
What are the three main factors for negative pleural pressure results?
1: the natural tendency of the lungs to recoil
Due to their great elasticity, the lungs tend to assume the smallest size possible at any given time
2: the surface tension of the alveolar fluid
The fluid film acts to draw the alveoli to their smallest size
Both of these factors act to collapse the lungs
The third factor counteracts these forces:
3:the surface tension created by pleural fluid in the pleural cavity
Plural fluid secures the pleurae together in the same way a drop of water holds two piece of glass together, it lets the glass slip from side to side, however, separating them will require extreme force. In the same way, the lungs are held tight against the thoracic wall but are allowed to move up and down against it
What are the two stage of pulmonary ventilation?
Inspiration
Expiration
What process govern breathing
Breathing is a process governed by volume changes that lead to pressure changes which result in the flow of gases
V——-> P———> F(flow of gases)
The relationship between pressure and volume in the lungs is given by ….
Boyles law
States that at constant temperature, the pressure of a gas varies inversely with its volume i.e. as the volume decreases, the pressure increase
These principles of gaseous flow and pressure/volume relationships provide the basis of pulmonary ventilation
What is the basic principle of inspiration?
Increase the volume of the thoracic cavity, hence causing a pressure gradient, down flows air i.e. into the lungs
Increasing the volume of the thoracic cavity is accomplished by contraction of the diaphragm and the external intercostal muscles
What muscles are involved during respiration?
1: diaphragm
Contracts and flattens out, moving the rib cage out
2: internal intercostal muscles:
Contracts and lifts the rib cage up and pulls the sternum forward
This mechanism expands the thoracic cavity, increasing its volume and therefore drawing air into the lungs, down the pressure gradient
What is the basic principle of expiration?
Inspiration muscles relax and resume initial resting length, causing the rib cage to descend and lungs to recoil. This results in a decrease in thoracic and inter pulmonary volumes
Overall, this compresses the alveoli and increases the intrapulmonary pressure, forcing gases to leave the lungs
Mostly a passive process at rest, however can become active via the use of abdominal and intercostal muscles
Describe the pressure inside the lungs during inspiration and expiration and explain how this helps respiration
Inspiration
The volume of the lungs increases
The pressure on the outside is higher than the pressure inside
So the pressure inside falls and air flows in
Expiration:
The volume of the lungs decreases
The pressure inside of the lungs is higher than the pressure outside of the lungs
So the inside pressure rises and the air flows out
What are physical factors influencing pulmonary ventilation
The flow of air in and out of the lungs in primarily mediated by the contraction and relaxation of the various respiratory muscles
However, the passage of air movement also presents with some resistance, such as:
- respiratory passageway resistance
- lung compliance and elasticity
- alveolar surface tension forces
What is respiratory passageway resistance?
The biggest resistance to air is friction or drag, which is encountered in the respiratory pathway (mouth, trachea, bronchioles)
As a general rule:
Gas flow = pressure gradient / resistance
What is the equation for gas flow
Gas flow = pressure gradient / resistance
What does lung compliance mean?
Lung compliance is the ease by which the lungs can be expanded
Specifically, lung compliance (CL) is a measure of the change in lung volume (triangle VL) that occurs with a change in the intrapulmonary pressure (triangle P)
Change in lung compliance = change in volume divided by change in intrapulmonary pressure
The more the lung expands for a given rise in pressure, the greater the compliance
What factors influence lung compliance?
Factors which influence lung compliance:
- influences that reduce the natural resilience of the lungs, such as fibrosis
- blockages of the bronchi or smaller respiratory passageways
- increase in the surface tension of the fluid film in the alveoli
- impairments in the flexibility of the thoracic cage
What factors make up lung elasticity
Lung distension is required for normal inspiration
Lung recoil is essential for normal expiration
These two favours make up lung elasticity
What is surface tension of the alveolar surface?
Surface tension:
- gas-liquid boundary
Liquid molecules are more strongly attracted to each other than to the gas- this is surface tension
Draws liquid molecules closer together
Resists any force that tends to increase the area of the surface
Surface tension on the walls of the alveolar help to keep them to their smallest size
This aids in expiration
This surface tension is produced by a film of fluid called surfactant, a detergent like lipoprotein by the type II alveolar cells
What is used to measure lung volume and capacity?
A spirometer
How does a spirometer measure respiratory volumes?
Tidal volume: the amount of air that moves in and out of the lungs with each breath (around 500ml)
Inspiration reserve volume : the amount of air that can be inspired forcibly beyond the tidal volume (around 2100 to 3200ml)
Respiratory reserve volume: amount of air that can be expired following tidal expiration (roughly 1000 to 1200ml)
Residual volume: the amount of air left in the lungs following the realise of the expiratory reserve volume (around1200ml)
How does a spirometer measure respiratory capacities?
Inspiratory capacities: the total amount of air that can be expired following tidal expiration
Functional residual capacity: the amount of air remaining in the lungs after tidal expiration
Vital capacity: the amount of exchangeable air (roughly 4800ml)
Total lung capacity : sum of all the lung volumes
What is dead space?
Anatomical dead space = the air left in the lungs following expiration (150ml)
Alveolar dead space: air left in the alveoli following expiration
Total dead space: anatomical dead space plus the alveolar dead space
What are the two tests to determine pulmonary function?
Forced vital capacity = measure the amount of gas expelled when a subject takes a deep breath and then forcefully exhales maximally and as rapidly as possible
Forced expiratory volume: measure the amount of air expelled during specific time intervals of the forced vital capacity test. Healthy lungs with expel about 80% of the total air within 1 second
What role is played by air pressure in breathing? Intra-pleural and intrapulmonary
See lecture notes
Describe the mechanics involved in breathing, inspiration and expiration
See lecture notes
Outline the physical factors influencing pulmonary ventilation
See lecture notes
Describe the outcomes of respiratory volume and pulmonary function tests
See lecture notes
How does gas exchange occur in the body?
Gas exchange occurs in the body by:
Bulk flow of gases
Diffusion of gases through tissue
Define Dalton’s law of partial pressure
The total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture. Further, the pressure exerted by each gas, its partial pressure, is directly proportional to its percentage in the total gas mixture
An example of Dalton’s law of partial pressure:
Air contains 78.6% nitrogen (N2) and 21% oxygen (O2) gas. Atmospheric pressure is 760mmHg. What is the partial pressure exerted by N2 and O2?
N2 = (78.6/100) x 760 = 597 mmHg
O2= (21/100) x 760 = 159 mmHg
Define Henrys law
When a mixture of gases is in contact with. A liquid, each gas will dissolve in the liquid in proportion to its partial pressure
Therefore, the greater the concentration of a particular gas in the gas phase, the more and the faster it will go into solution in the liquid
The amount of gas dissolved in solution is directly proportional to the pressure of the gas over the solution
What factors influence the exchange of gasses at the levels of the alveoli?
Partial pressure gradients and gas solubility:
- steep O2 gradient in alveoli, more O2 in alveoli relative to pulmonary blood supply. O2 moves from the alveoli into the blood, equilibrium is reached within 0.25 seconds
- a CO2 gradient also exists, higher CO2 within the pulmonary blood supply and lower CO2 within the alveoli means that CO2 leaves the blood supply and enters the alveoli for expiration
- CO2 is 20 times more soluble than oxygen in plasma and alveolar fluid than O2. Therefore, CO@ is able to leave the blood faster and in the presence of a much shallower concentration gradient
Describe the thickness of the respiratory membrane:
Respiratory membrane is the membrane between the alveoli and the pulmonary capillaries
Normally 0.5 to 1 micrometers thick
This thin membrane makes gaseous exchange very efficient
Pneumonia is an increase in membrane thickness
How does pneumonia affect the respiratory membranes thickness?
It increases it, making gaseous exchange less efficient
Describe how surface area affects gaseous exchange
The greater the surface area, the greater the gaseous exchange
In an adult human the total surface area of the lungs is approximately 140m2
What is emphysema?
A pulmonary disease characterised by the breakdown of the alveolar walls, this reduces the surface area for gaseous exchange
What is perfusion coupling in regards to ventilation?
Efficient gaseous exchange requires a close match/coupling between ventilation (amount of gas reaching alveoli) and perfusion (blood flow in pulmonary capillaries)
Decreased oxygen in the alveoli results in the dilation of the pulmonary capillaries, hence increasing the amount of O2 loading
An increase in carbon dioxide in the alveoli results in dilation of the bronchioles, hence increasing airflow out of the lungs
What does gas exchange within internal respiration mean?
At a systemic level, gaseous exchange takes place by simple diffusion down concentration gradients of specific gases
Basically, with metabolising organs, O2 concentrations are low and CO2 concentrations are high
Arterial blood supply innervations organs will have to increase O2 and decrease CO2
Therefore, O2 will enter the organs and CO2 will leave the organs
How is oxygen carried b the blood?
Bound to haemoglobin within red blood cells
Dissolved in plasma
Describe the structure of haemoglobin
Haemoglobin (Hb) is composed of 4 polypeptide changes, each bound to an iron, containing a haeme group
Oxygen binds to the iron atoms, therefore one molecule of Hb can carry 4 molecules of oxygen
What is oxygen called when it binds to Hb?
Oxy-haemoglobin (HbO2)
What is haemoglobin called once it releases the oxygen?
Deoxy-haemoglobin (HHb).
Is the association and dissociation of oxygen and haemoglobin a reversible reaction?
Yes
lungs HHb+O2 ———————————> HbO2 + H+
What happens to haemoglobin once one molecule of oxygen binds to it?
Once one molecule of O2 has bound to Hb, a change in the structure of Hb occurs. This facilitates the binding of another 3 O2 groups i.e. it gets easier to bind the other groups once one molecule has bound
The same is true when O2 is offloaded, once the first molecule has come off, the others are much easier to remove
How does the partial pressure of O2 influence Hb saturation?
The amount of oxygen released by Hb is dependant on the amount of oxygen in the tissue i.e. the partial pressure of oxygen (Po2) in the tissue
Best described as a graph plotting oxygen saturation against the Po2
This graph is called the oxygen dissociation curve
What are the key points gained from the oxygen dissociation curve?
A small drop in Po2 results in a large release of O2 from Hb . This is shown by the steep part of the curve
At high saturation’s, it takes a large drop in Po@ to release O2
What can cause shifts in the oxygen dissociation curve?
Temperature - increase in temperature enhances O2 offloading
pH; a decrease in pH enhances O2 offloading
Pco2
These factors all effect oxygen saturation and influence the structure of Hb
Bohr effect:the acceleration of O2 unbinding where it is needed
The above factors all alter in metabolising organs
What is the Bohr effect?
The cancellation of O2 unloading where it is needed
Describe the process of carbon dioxide transport
CO2 is transported by the following routes:
- dissolved in plasma (7-10% of CO2)
- chemically bound to Hb in red blood cells - 20 to 30% as carbaminohaemoglobin
- as bicarbonate ions in plasma (60-70% of CO2 converted to bicarbonate ions (HCO3)
CO2 + H2O ———>H2CO3 ————> H+ + HCO3
What is carbonic anhydrase?
Catalysis the reaction between CO2 and H20 to form carbonic acid
What is the chloride shift?
As HCO3 moves out of the red blood cells, Cl- ions move in, to balance the ion exchange
Discuss how carbon dioxide is transported in blood:
CO2 diffused into the bloodstream
7% remains dissolved in plasma (as CO2)
93% diffuses into red blood cells then:
23% binds to Hb, forming carbaminohaemoglobin, HbCO2
70% is converted to H2CO3 by carbonic anhydrases
The 70% that has been converted to H2CO3 dissociates into H+ and HCO3-
The H+ is removed by buffers
HCO3 moves out of the red blood cell in exchange for Cl-
Describe the two basic gas laws involved in gaseous exchange
See lecture notes
Describe the factors influencing the exchange of gasses within alveoli and peripheral organs
See lecture notes
Explain the mechanisms used to transport oxygen around the body
See lecture notes
Interpret the oxygen dissociation Curve and describe any factors that influence its shape
See lecture notes
Describe how carbon dioxide is transported around the body
See lecture notes
How is breathing regulated at rest?
At rest, it is regulated subconsciously by the brain
The regions of the brain that are responsible are located in the brain stem
What regions of the brain regulate breathing?
Reticular formation:
Medulla
Pons
Clusters of neuron in two areas of the medulla oblongata appear to be critically important to respiration. What are these two areas?
Dorsal respiratory group (DRG)
Cluster of neurons that are located dorsally near the root of the cranial nerve
Ventral respiratory group (VRG)
Network of neurons that extends within the ventral brain stem from the top of the spinal cord to the pons-medulla junction
What are the actions of the DRG?
Pace setting respiratory centre, hence termed the inspiratory centre
When DRG neurons fire, nerve impulses travel along the phrenic and intercostal nerves
This excites the diaphragm (phrenic nerves) and intercostal muscles (intercostal nerves)
As a result, the thorax expands and air rushes into the lungs
This on-off cycle from the DRG repeats to generate 12 to 15 breaths a minute, this normal rate is referred to as Eupnea
During hypoxia (reduced O2 in the blood) the DRG generates gasping in order to increase O2.
Overdoses of sleeping pills, morphine or alcohol can completely suppress the medulla inspiratory neurons leading to a stop in respiration
Expiration occurs passively as the inspiratory muscles relax and the lungs recoil. The DRG is dormant at this time
What are the actions of VRG?
There action of VRG in respiration is not well understood
It is thought that the VRG plays a role in forced breathing, especially during expiration
For example during exercise
What is the function of the pons respiratory centres?
Pons centres can modify the activity of medullary neurons
These centres act to smooth the transition between inspiration and expiration
The pneuomtaxic centre in the superior pons seems to exert an inhibitory effect on the medulla i.e. slowing down respiration
How is breathing rhythm generated?
It is obvious that breathing occurs in a very rhyming matter
However, it is unclear how this rhythm is generate
At present, one thing is sure - the medullary centres themselves are capable of maintain the normal rhythm of breathing
Why does the rate and depth of breathing change?
The rate and depth of breathing is modified depending on the demands of the body
For example, exercise, anticipation and sleeping
What are the three receptors that can influence breathing?
Pulmonary irritant reflexes:
Occur when receptors in the lungs are activated by inhaled debris such as dust, lint and smoke. This initiates a cough reflex
Hering-Breuer reflex: Stretch receptors (mechanoreceptors) in the visceral pleura are activated during inhalation and report to the medulla which then, in turn, shuts down DRG activation including exhalation
Chemoreceptors:
Respond to changes in levels of CO2, O2 and H+ ions in arterial blood
Location of chemoreceptors:
Central chemoreceptors: found in the medulla of the brain stem
Peripheral chemoreceptors: found in the carotid arteries within the neck
How are CO2 levels controlled?
CO2 levels are very closely regulated
CO2 levels are controlled within 7% of the normal boundary by homeostatic mechanisms
CO2 levels are monitored by the central chemoreceptors via diffusion into the cerebrospinal fluid (CO2 forms H2CO3 causing an increase in H+ ions)
A rise in CO2 levels is called hypercapnia and results in hyperventilation to enhance CO2 clearance
The peripheral chemoreceptors are sensitive to levels of arterial O2, these are located in the aortic and carotid bodies. For a response to a drop in O2 levels to occur, arterial O2 must fall to about 60% of its normal level. This will result in increased ventilation
Drawn and label a digram showing the regulation of carbon dioxide levels
See lecture notes
How are H+ levels controlled?
Regulated by peripheral chemoreceptors
An increase in H+ ions can result from:
Increase CO2 levels
Increase in lactic acid e.g. following exercise
The lungs try to compensate by increasing ventilation to eliminate CO2, hence reducing arterial H+ ions
What are the effects of exercise on the respiration you system?
Effects of exercise:
Working muscles consume large amounts of O2 and produce larger amounts of CO2
Breathing becomes deeper and more vigorous resulting in ventilation increasing by ten to twenty times. This pattern of breathing is hypernea
O2 and CO2 levels remain consistent as supply is equal to demand
Describe ventilation rhythms during exercise
At first; ventilation abruptly increases
This is due to:
- psychic stimuli (anticipation of exercise)
- simultaneous cortical motor activation of skeletal muscles and respiratory centres
- proprioceptors in moving muscles, tendons and joints
Followed by a gradual increase
At the end of exercise, ventilation declines suddenly
What effects does high altitude have on respiration?
At high altitudes e.g. up on mountains; air density and O2 concentrations fall
At these heights, your body initially presents with the following symptoms as it acclimatises:
- headaches
- nausea
- dizziness
A decrease in O2 concentrations causes:
Central chemoreceptors to become more sensitive to CO2
Direct stimulation of peripheral chemoreceptors
Results in increase ventilation. After a few days, the rate of respiration stabilises to 2 to 3 litres/minute higher than sea level
This also reduces CO2 and reduces haemoglobin (roughly 60% at 6000m)
Slow increase in production of red blood cells
How many people do respiratory diseases kill?
1 in 5
Respiratory disease is most common in …
Children
What are some causes of respiratory disease?
Genetics
Nutritional
Poverty
Environmental factors
Smoking
What is asthma?
Asthma is an inflammatory condition of the distal airways provoked by triggers, resulting in reversible bronchi-constriction
What can trigger asthma?
Tobacco smoke
Dust mites
Air pollution
Pests
Mold
What are non specific symptoms of asthma?
What are pathological changes of asthma?
Non specific symptoms: Cough Wheeze Breathlessness Tight chest
Pathological changes: Excess mucus production Mucosal oedema Broncho-constriction Bronchial hyper-reactivity
What is a treatment for asthma?
Corticosteroids
What are corticosteroids?
They reduce airway inflammation
Mainstay of asthma management
Onset of action is 3 to 7days
Regular use inhalers: beclometasone, budesonide, fluticasone
Exacerbation: oral prednisolone, morning dose to mimic circadian rhythm for 3 to 5 days
Prednisolone reduces airway inflammation by inhibiting infiltration of inflammatory cells and reduce oedema by an action on by an action on vascular endothelium
What happens if you take prednisolone with anti-convulsants?
Decreased steroid effects
What happens if you take prednisolone with anticoagulants?
Activity of anticoagulant can increase of decrease
What happens if you take prednisolone with antidiabetics?
Reduce hypoglycaemic effect
What happens if you take prednisolone with antihypertensives?
Reduced hypertensive effect
What happens if you take prednisolone with diuretics?
Reduced diuretic effect
What happens if you take prednisolone with ciclosporin?
Increased steroid effect
What happens if you take prednisolone with vaccines?
Reduced immune response
Name the regions of the brain that regulate respiration
See lecture notes
Describe the roles played by DRG and VRG in regulating the rate of respiration
See lecture notes
Describe the various receptor types that can be used to regulate/influence the rate of breathing
Sere lecture notes
Describe the mechanisms used to regulate arterial O2, CO2 and H+ ion concentrations
See lecture notes
Describe the adjustments made by the respiratory system during exercise and at high altitudes
See lecture notes
Outline the use of corticosteroids in asthma treatment
See lecture notes
