Respiratory System Flashcards
What type of epithelium lines alveoli?
Simple squamous
What do the upper airways consist of?
The nasal cavities
Larynx
Nasopharynx
Laryngopharynx
How is the upper respiratory tract protected from cold shock and drying?
Inspired air passes through warm plates of conchae where air is warmed and humidified
Why does open air breathing take over during exercise
Nasal passages are narrow and complex and have a high resistance to air flow and during exercise, respiratory muscles can’t propel air through the nose fast enough
Where are paranasal sinuses located?
On the lateral walls of the nasal cavities
What is the purpose of the paranasal sinuses?
Crumple zone in trauma
Reduce weight of face
Voice resonators
Protect sensitive dental roots and eyes from temperature fluctuations
What do the lower airways consist of?
Trachea, bronchi and bronchioles
What is the purpose of the pleura?
Allow lungs to slide smoothly within pleural cavity during breathing
What are the surfaces of the lung?
Costal
Inferior (diaphragmatic)
Mediastinal
What is the highest part of the lung?
Apex
Lying 2-3 cm above clavicle in the root of the neck
What is the costo-diaphragmatic recess?
Lowest part of pleural cavity which contains no lung during expiration
What is minute ventilation?
Volume of air expired in one minute
What is the respiratory rate?
Frequency of breathing per minute
Why may alveoli not be able to take place in gas exchange?
Hypoperfused
What is the approximate tidal volume?
600 ml
What is the approximate inspiratory reserve volume?
2.7 L
What is the approximate expiratory reserve volume?
1.3 L
What is the approximate residual capacity?
1.2 L
What is the approximate total lung capacity?
6 L
What are anatomical dead spaces?
Nasal cavity
Larynx
Pharynx
How would you increase alveolar ventilation?
Increase depth of breathing
Why are the lungs always under negative pressure?
Due to the natural recoil of the lungs away from the chest wall
What is the pleural pressure of the lungs?
- 5cmH20
- 3 at base
- 7 at apex
What is a haemothorax?
Accumulation of blood in the pleural cavity
Why does a haemothorax pose a problem?
Blood gradually fills into the pleural cavity which gradually reduces the area in which the lungs can expand. This leads to gradually more effort required to inhale a certain volume.
The overall volume achievable is reduced
Why does a pneumothorax pose a problem?
The negative pressure caused by the inward recoil of the lungs and outward recoil of chest wall is compromised.
The resistance between the two forces will disappear
Why is the FVC in restrictive disorders decreased?
Air trapping due to emphysema
How can peak expiratory flow measurement distinguish between asthma and cold?
cold measurements are stable whereas asthma is variable
Where does a flow volume loop begin on the x axis?
The total lung capacity
What measurements are higher in obstructive lung disease?
Residual volume and Total lung capacity
What measurements change in restrictive lung disease?
Total lung capacity is lower
What can cause variable extra thoracic obstruction?
Obstruction in upper airways
What can cause variable inter thoracic obstruction?
Obstruction in trachea
Why does the base of the lung ventilate more readily?
The effect of gravity on transpulmonary pressure makes the base more compliant
What else does gravity effect?
The distribution of blood flow, blood will perfuse the base more as it has the route of least resistance
How are V/Q ratios interpreted?
High V/Q- poor perfusion
Low V/Q- poor ventilation
What is Henry’s law?
At a constant temperature, the volume of gas that dissolves in a certain volume and type of liquid is proportional the the partial pressure and solubility of the gas in equilibrium with the liquid
What is Dalton’s law?
The pressure of a mixture of gases is the sum of the partial pressures of all gases in the liquid?
What is Fick’s law?
Molecules diffuse from an area of high concentration to low concentration at a rate that is directly proportional to the surface area of gas exchange, the solubility of the gas, the concentration gradient and inversely proportional to the exchange surface
What is Boyle’s law?
The volume of a gas is inversely proportional to partial pressure
What is Charles’ law?
The volume of gas is directly proportional to temperature
What does inspired air consist of?
- 2 % Nitrogen
- 9 % Oxygen
- 9 % Argon
- 04 % Carbon dioxide
- 01 % inert gases
What are the inert gases?
Xenon, helium, hydrogen, neon
What is barometric pressure at sea level?
101.3 kPa
What is inspired air humidified to?
6.3 kPa
What are allosteric proteins?
Proteins that change their change depending on what ligands are bound or unbound
What are the different glob in chains?
Alpha
Beta
Delta
Gamma
Where is the harm group attached to the protein chain?
The proximal histamine residue
What are the different variations of haemoglobin?
HbA - 98 % 2 alpha 2 beta
HbA2 - 2% 2 alpha 2 delta
HbaF - (foetal) trace amounts 2 alpha 2 gamma
Why is haemoglobin toxic?
Can cause renal failure by attacking renal tubule epithelia
What is the phenomenon where oxygen binds to haemoglobin, changing the conformation and allowing more oxygen to bind?
Co-operativity
How does oxygen bind promote oxygen unloading?
It affects the active site between two beta subunits for the binding of 2,3-DPG which is a co-factor in red blood cell energy production.
This cofactor binds to the beta subunits and pushes haemoglobin into the tense state to promote oxygen unloading
What will cause the Bohr effect? (rightwards shift)
Acidosis
Hypercapnia
Increased temperature
Increased 2,3-DPG
What is normal P50?
3.3kPa
How much greater is the affinity of Hb for CO than oxygen?
250x
Why does Hb binding to CO cause problems?
Reduces number of sites on Hb that can bind to oxygen
CO pushes Hb into tense state so it is unable to unbind from oxygen
What effect does CO have on the oxygen dissociation curve?
Pushes it downwards and to the left
What is methaemoglobin?
When the Fe2+ ligand becomes oxidised to the Fe3+ state and cannot bind haem
What is familial methaemoglobinaemia?
A genetically recessive disease presenting with a blue tinge to the skin
What are the differences between myoglobin and haemoglobin?
Myoglobin is monomeric
Myoglobin is principally a storage molecule found in myocytes
What is the route of oxygen during oxygenation?
From alveolar space, pulmonary epithelial cells, interstitial space, vascular endothelial cells, into the plasma, into red blood cells where it binds to Hb that is not yet saturated
Why does aqueous carbon dioxide pose a problem?
Will bind to H20 to form weak carbonic acid which will dissociate into protons and bicarbonate ions
What prevents the intracellular decrease in pH?
Excess protons are buffered by globin molecules
How is carbaminohaemoglobin formed?
Carbon dioxide binds to the amine group at the N-terminal of the Hb molecule
What is the Halade effect?
Describes the relationship between the saturation of oxyhaemoglobin and the formation of carboaminohaemoglobin
What is hypoxia?
Low oxygen environment
What is hypoxaemia
Low blood oxygen level
What is the oxygen cascade?
Reduction in partial pressure of oxygen from atmospheric air to respiring tissues
What are the determinants the effects the oxygen cascade
Ventilation/perfusion matching
Alveolar ventilation
Cardiac output
Diffusion capacity
What are the adaptions to prevent the initial responses of hypobaric hypoxia?
Renal compensation- bicarbonate improves the pH and returns the oxygen dissociation curve to the correct place
Increase 2,3-DPG to increase oxygen unloading
What is a long term response to hypobaric hypoxia?
Secondary erythrocytosis. Hypoxia stimulates kidneys to release erythropiotein, leading the the bone marrow to produce red blood cells at a higher rate
What are the results of HAPE
Pulmonary artery vasoconstriction
Pulmonary artery hypertension
Capillary leakage
What treatment is available for HAPE?
Nifepidene
When do the lungs begin to develop from the tracheal bud?
4-5 weeks gestation
When is bronchial branching complete?
16 weeks gestation
When is alveolar development completed?
8-10 years of age
What is more important in malformation?
The timing of the insult rather than the nature
What supplies bronchial buds in utero?
Systemic vessels
What is agenesis?
When the developing lung does not develop
What are local lesions?
When the developing lung develops extra buds which present as lesions
What factors influence lung development?
Hox genes Maternal nutrition Thoracic cage volume Paracrine and autocrine interactions Growth factors Lung liquid positive pressure Amniotic fluid volume Transcription factors
Why is the lung inactive in the womb?
No air therefore no need
Why does maternal smoking result in reduced lung function for the baby at birth?
Affects the pacemaker which causes pulsation and respiratory movements. Inflammation has a greater effect and the baby will be more susceptible to disease
What is the umbilical vein?
Connects placenta to foetal circulation
What does the umbilical vein carry?
Blood to ductus venosus which takes blood to inferior vena cava
OR blood directly to the liver via the hepatic portal vein
What prevents blood from entering the pulmonary circulation in utero?
The foramen ovale is a whole that connects the right atrium to the left atrium which blood flows through
Blood is able to do this as the right atrium is at a higher pressure than the left
What does the ductus arteriosus connect?
The pulmonary artery to the arch of the aorta
What happens at birth?
There is massive CNS stimulation
Placental circulation is cut off and systemic pressure rises
Under the influence of prostaglandins, what do the ductus arteriosus and foramen ovale form?
Ligamentum arteriosum
Fossa Ovalis
What causes the fluid in lungs to recede?
Breathing
Expelled via mouth
Absorbed by lympatics
Where does superfactant come from?
Lamellar bodies in type II pneumocytes
What is trachoesophageal fistulae?
An opening between the oesophagus and trachea
What disease can occur in premature infants?
Respiratory distress syndrome (hyaline membrane disease)
Outline RDS
Deficient superfactant which decreases lung compliance and increases dead space.
Alveolar collapse leading to hypoventilation causing hypoxia and acidosis.
This leads to pulmonary vasoconstriction and pulmonary pressure increases. Right to left shunting.
What is shunting?
Poor ventilation with normal perfusion
What does mucus consist of?
Mucin proteins
proteoglycans
glycosaminoglycans
What are the parts of mucus?
Sol face (thin overlying the cells) Gel phase (thick overlying the lumen)
How does mucus protect lung tissue?
Contains alpha 1 anti trypsin. Which is a neutrophil protease inhibitor so any proteases in the lumen don’t affect lung tissue
How does mucus combat oxidants?
Contain antioxidants including:-
Uric acid
ascorbic acid
Glutathione
What is goblet cell hyperplasia?
Common in smoker
Number of goblet cells at least doubles and secretions increase
Mucous thickens
Can take cigarette smoke particles but becomes more habitable to micro-organisms
How do cilia beat?
Metasynchronously
Where are the tips of the cilia?
Sol phase of the mucus
What is the appearance of cilia in smokers?
The numbers are depleted
Appear in bronchioles
Beat asynchronously
Can’t transport thickens mucous
What is the main function of phase 1 enzymes?
cytochrome p450 oxidase
Protect against foreign material
What problems do phase 1 enzymes cause?
They convert pre-carcinogens into carcinogens
What is the ratio of type 1 to type 2 epithelial cells?
1:2
What are type 1 epithelial cells?
Cover 95% of the alveolar surface
Present for efficient gas exchange
What are type 2 epithelial cells?
type II pneumocytes containing lamellar bodies
and precursors to the type 1 cell
What cells are more present in alveolar fibrosis?
Type II cells
Fibroblasts
What are alveolar macrophages?
They make up 90% of phagocytic cells in lung
Phagocytose debris and microorganisms in the lung
Send messages to the blood and lymphatic system to recruit other leukocytes during infection
How many neutrophils in large airway normally and in a smoker?
30%
70%
Where is the involuntary centre located?
Metabolic centre
Medulla
Where is the voluntary centre located?
Behavioural centre
motor centre in the cerebral cortex
What overrides the behavioural centre?
The metabolic centre
What effects the metabolic centre
Limbic system
Frontal cortex
Sensory inputs
How does the medulla sense increased carbon dioxide?
Proton receptors in carotid bodies
Directly from extracellular fluid it is bathed in
What is the pre-Botzinger complex?
nucleus in the brain that determines the rhythm of the lung
What is chemosensitivity?
A change in minute ventilation due to a change in PaCO2
What causes acute respiratory acidosis?
Hypoventilation
What causes chronic respiratory acidoses?
When the correction mechanisms for hypoventilation are not enough ie. minute ventilation being increased, to increase 02 and correct pH
What is metabolic acidoses?
Excess production of protons by the metabolism
What is renal compensation?
Excreting weak acids and retaining chloride ions in a bid to reduce the strong ion difference
What is metabolic alkalosis?
Excess production of Hc03-, reducing the proton concentration
How is alkalosis corrected?
Hypoventilation- increasing ventilation
Long term renal compensation where chloride ions are excreted and protons are retained so the strong ion difference is increased
What are the acute and chronic causes of central hypoventilation?
Acute- metabolic centre poisoning due to drugs
Chronic- disease of the metabolic centre, mountain sickness
What are the acute and chronic causes of peripheral hypoventilation?
Acute- muscle relaxants and myasthenia gravis
Chronic- neuromuscular disease, neuromuscular weakness
What disease is a mix of both central and peripheral hypoventilation?
COPD
What are examples of hyperventilation conditions?
Chronic anxiety
Pulmonary vascular disease
Chronic hypoxaemia
Excess protons
What is the predominant supply of the respiratory system?
Parasympathetic nervous system via the vagus nerve?
What does the sympathetic nervous system have an effect on?
The adrenal glands, secreted catecholamines
What does parasympathetic activation cause?
Smooth muscle constriction
Mucus secretion
What is airway remodelling?
Basement membrane will thicken
Epithelium will become more fragile
Increased mucus secretion
More congested airways
What does activation of beta receptors cause?
Bronchoconstriction
What is the precursor of squamous cell carcinoma?
Squamous cell metaplasia leads to dysplasia
Leads to carcinoma-in-situ
Leads to squamous cell carcinoma
What is the precursor of adenoma?
Atypical adenomatous hyperplasia
What are the clinical features of lung cancer?
Hoarseness of voice Chest pain Cough Clubbing of nails May be asymptomatic Haemoptysis Dyspnoea
What does smoking cause?
Chromosal translocation
Formation of a fusion gene which inhibits the natural arrest of G1 causing a cell to unto mitosis uncontrollably
Also atopsis is halted
How many lung cancers does non-cell carcinoma account for ?
75%
Give examples of non cell carcinoma
Adenocarcima Large cell carcinoma Squamous cell carcinoma Broncho-alveolar carcinoma Anaplastic carcinoma
Which type of lung cancer is more responsive to chemotherapy?
Small cell carcinoma
Which type of lung cancer is prevalent in non smokers?
Non small cell carcinoma - adenocarcinoma
What organs should have a CT scan for staging?
Thorax, liver, adrenals
What is stage TX
The primary tumour can not be assessed
What stage is T0
No evidence of primary tumour
What stage is Tis
Carcinoma in situ
What stage is T1
Tumour is 3cm or less in dimension and is surrounded by the lungs or visceral pleura
What stage is T2
Tumour is more than 3cm and invades the pleura, involves main bronchus, is 2 cm or more distal to the carina, involves atelectasis
What stage is T3
Tumour of any size invades, parietal pericardium, diaphragm, chest wall, Is less than 2cm distal to carina but does not invade it
What stage is T4
Tumour invades, heart, medistinum, great vessels, trachea, oesophagus, vertebral body
Describe NX
Regional lymph nodes cannot be assessed
Describe N0
No regional lymph node metastasis
Describe N1
Involves ipsilateral hilar node
Describe N2
Ipsilateral, mediastinal lymph node
What are risk factors of lung cancer?
Smoking
Asbestos exposure
Radiation
What is paraneoplastic syndrome?
What is caused by the effects of the tumour
Secondary effects due to the presence of the tumour itself
Give examples of paraneoplastic syndrome
Cushings- ACTH release due to ectopic lung
Hypoatronaemia -adh release
Hypocalcaemia - parathormone
What is mesothelioma?
Malignant tumour of the pleura due to asbestos exposure
Why is mesothelioma usually fatal?
Has a long lag phase so symptoms take a long time to present?
Which gender is mesothelioma more common in?
Males
Which centre controls breathing during sleep?
Metabolic centre via the medulla
What are the two main stages of sleep?
Rapid eye movement sleep
Non REM
What causes the eyes to move during REM sleep?
The body is paralysed and relaxed due tot he release of neurotransmitters that render motor neurones immobile.
The only things that can move are the eyes and diaphragm
What is the purpose of REM sleep
To consolidate memory
What are the changes observed between wakefulness and sleep?
Reduced tidal volume
Reduced ventilatory rate
Reduce oxygen saturation
Reduced alveolar ventilation
What is the apnoeic threshold?
The level of PC02 that must be exceeded to stimulate respiratory centres during sleep. If the levels are below the threshold apnoea will occur
What is central sleep apnoea?
When one continuously stops breathing during sleep because impulses stop being sent to the brain because of hypocapnia.
If hypocapnia occurs, it will not be corrected and the CO2 reserve will decrease leading to apnoea
The p02 will decrease and pC02 increases leading a person to wake up as a result of discomfort
What causes central sleep apnoea?
Lesion in the brain where breathing is controlled or can be congenital
Which muscles cause stiffening of the pharynx and prevention of its collapse?
Tongue
Levator palitini
Tensor palatine
Why is there difficulty in breathing whilst sleeping in COPD patients?
Accessory muscles will be paralysed
P02 is already low
How is heart failure associated with central sleep apnoea?
Causes pulmonary congestion which irritates the J-receptors leading to chronic hyperventilation causing a patient to get closer to the apnoeic threshold
What is the purpose of a cough?
A defence mechanism which protects the lower respiratory tract from foreign material and mucus build up
What initiates a cough?
Irritant receptors sense irritants such as mucus and dust and the cough reflex is initiates via the superior laryngeal nerve to the vagus of the brain
Where are irritant receptors most numerous
Posterior wall of trachea and present on airway epithelium
Pharynx
Stomach
Diaphragm
What neurotransmitters are involved in relaying information to the cough centre?
GABA
Serotonin
What can be used to suppress a cough?
Opiates
Describe the mechanics of a cough
Begins with the inspiratory phase and then the closure of the glottis. This causes pressure to increase and the glottis opens after a certain point which forces air out during the expiratory phase
What are causes of acute cough?
Common cold Post nasal drip Throat clearance Nasal blockage Nasale discharge
How can gastric reflux cause cough?
Protons can travel into oesophagus to pharynx and enter respiratory system where they will act on cough receptors
How is the cough for gastric reflux treated?
Proton pump inhibitors to cease the release of protons
What are the different ways to treat cough?
Narcotic and non-narcotic cough medicine
Removing inflammation through use of corticosteroids
What are the neural pathways for sensory input for lungs, airway and chest wall?
Vagus nerve
Spinal nerve
What is the neural pathway for the sensory input of the nose?
Trigeminal nerve
What are the neural pathways for the sensory input of the pharynx?
Glossoparyngeal nerve
Vagus nerve
How does pain reach its target site?
Goes through the thalamus, spino-thalamic tract, to the dorsal horn of the spinal nerve
Where are the dermatomes of the diaphragm situated?
Shoulder
What may cause pleural pain?
Pulmonary infarction and pneumonia
What may cause chest pain in non respiratory disease?
Cardiovascular disorder
Musculoskeletal
Gastrointestinal
Psychiatric
Which two circulations does the lung have?
Bronchial and pulmonary
Where do bronchial arteries arise from?
Thoracic aorta
Where do bronchial arteries converge?
Pulmonary vein
Describe the pulmonary circulation
It is a low resistance, high capacity circuit
What are the purposes of pulmonary circulation?
Gas exchange
Metabolism of vasoactive substances
Filtration of the blood
What compounds are cleared due to the action of enzymes on the pulmonary epithelium?
Serotonin
Leukotreines
Prostaglandins
Noradrenaline
What acts as a filter of harmful emboli
Pulmonary microcirculation
How are air emboli, fat emboli and cancerous cells removed?
Air- diffuse out and removed via alveolar air spaces
Fat- broken down by the vascular endothelium
Cancer- removed via secondary metastasis
Give examples of shunts
Bronchial circulation
Formaen ovale
Ductus arteriosus
Atrial septum disease
How does the pulmonary circulation prevent a great increase in resistance during exercise?
Greater recruitment of capillary beds
Distension of the vessels
How do the adaptions of the pulmonary circulation to prevent an increase in resistance help?
Prevents oedema
Prevents an increase pressure on right ventricle
Slows velocity to ensure efficient gas exchange
What are the differences between systemic vessels and pulmonary vessels in the event of hypoxaemia?
Systemic vessels dilate
Pulmonary vessels constrict
What is more porous, systemic or pulmonary capillaries?
Pulmonary
What can cause oedema?
Increasing hydrostatic press
Reducing interstitial oncotic pressure
Increasing interstitial protein
Reducing lymphatic drainage
What are the consequences of oedema
Lungs become less compliant and therefor require more energy to be ventilated which can present with oedema.
Lead to bronchioles becoming swollen which increases resistance
Furthermore, if excessive oedema is present in the interstitial space then increases diffusion distance and impedes gas exchange
Outline resting respiration
Diaphragm contracts, compressing the abdominal cavity and decompressing the thoracic cavity.
Interpleural pressure decreases from -5cmH20 to -8cmH20.
Lungs expand to prevent a further decrease in inter pleural pressure
Alveoli expand to return to normal pressure
What allows the lungs to stretch?
Collagen
Elastin
What is elastance?
Tendency of lungs to return to their original volume after the removal of inspiratory forces
What is surface tension?
Tendency of water molecules to attract each other
What does pulmonary surfactant consist of?
Polar phospholipids (80%) Neutral lipids (10%) Protein (10%)
How does pulmonary surfactant prevent oedema?
During expiration, the alveoli decrease in size which causes a reduction in pressure in the interstitial space which will draw fluid out of the pulmonary circulation.
Surfactant limits the change in size of the alveoli
What are the causes of hypersensitivity?
Intolerance of food
Enzyme deficiency
Pharcological hypersensitivity
What causes the acute symptoms of ally?
IgE mediated immunological reactions cause mast cell degranulation which results in histamine release
What is atopy?
The heredity predisposition to produce IgE antibodies to common environmental allergens
Give examples of atopic diseases
Allergic rhinitis
Atopic Eczema
Asthma
Anaphylaxis
How are allergic tissue reactions characterised?
By the infiltration of Type 2 T helper cells and eosinophils
What is the allergic march
The progression from atopic dermatitis to allergic asthma
What mediates non atopic allergic diseases?
T cells
IgG
Give examples of non atopic diseases
Coeliac disease
Contact dermatitis
Extrinsic allergic alveolitis
Give examples of non-allergic hypersensitivity
Migraines
Bloating due to wheat intolerance
Enzyme deficiency
Irritable bowel syndrome
What can anaphylaxis cause?
Oedema
Uticaria
How would you treat anaphylaxis
With an epipen as is contain adrenaline to combat the histamine
What drugs are used to treat rhinitis?
Antihistamines
Topical corticosteroids
Give examples of histamine H1 receptor antagonists
Loratedine
Cetirizine
Fexofenadine
What is specific immunotherapy?
Administering increasing extracts of allergens of a long period of time
What are the pros and cons of specific immunotherapy?
Very effective in seasonal allergic rhinitis and lasts for a long time when administered over many years
However patients are at risk of developing general and possibly fatal anaphylaxis
What is the arrangement in cilia?
9 pairs of dyenin arms on the outside and two in the middle
What consists of cilia
Line the nose, middle ear, eustachian tube, line the bronchi as far as respiratory bronchioles
Form the tail of spermatozoa
What is dextrocardia?
When the heart is on the right hand side
What is Kartegeners syndrome?
When primary ciliary dyskinesia presents with bronchectasis, dextrocardia and chronic sinitus
How do viral infections affect mucociliary clearance?
Destroy ciliary cells
Produce more water mucus which are not easily cleared by cilia as they are not sticky
How does smoking effect ciliary epithelium cells?
Kills of cilia, causing ciliary dyskinesia, absent dyenin arms and compound cilia
Why is H influenza chronically present in smokers?
They have fimbriae, allow them to anchor themselves to epithelium and resist being swept away by cilia
What are present in the alveoli during pneumonia?
Cell debris
Fibrin
Bacterial invasion
Imflammatory cells
What is the shape of streptococcus pneumoniae?
Diplococcus
How does streptococcus pneumoniae cause harm?
Produces the toxin pneumolysin which punches holes into the alveolar cells which cannot regenerate therefore gas exchange is impaired
What is broncthetasis?
Localised and irreversible dilation of part of the bronchial tree which is due to the muscle and elastic tissue being destroyed
