Phase 1 - Week 8 (Respiratory System, Asthma), Phase 3 - Week 4 (Pneumothorax), Phase 3 - Week 5 (Spirometry, COPD) Flashcards
List the functions of the respiratory tract
- Ventilation
- Gas exchange
- Blood pH
- Air preparation
- Vocalisation
- Olfaction
- Protection + defense
List the sections of the respiratory tract
- Nose/mouth
- Pharynx
- Larynx
- Trachea
- Primary bronchi
- Secondary (lobar) bronchi
- Tertiary (segmental) bronchi
- Conducting bronchioles
- Terminal bronchioles
- Respiratory bronchioles
Pharynx
- Muscular tube lined with mucous membrane
- Joins nasal + oral cavities to oesophagus and larynx
List the parts of the pharynx
- Nasopharynx
- Oropharynx
- Laryngopharynx
Nasopharynx
- Nasal cavity -> oropharynx
- Separated from oral cavity by soft palate
- Receives Eustachian tubes (auditory/pharngotypanic) from inner ear
- Contains pharyngeal tonsils - protect against inhaled pathogens
Oropharynx
- Between soft palate + upper border of epiglottis - posterior to oral cavity + tongue
- Contains palatine, pharyngeal + lingual tonsils
- Palatine = 2 masses of lymphatic tissue, posterior oral cavity between glossopalatine + pharyngopalatine arches
- Pharyngeal = patch of lymphatic tissue in posterior wall of nasopharynx, most prominent in children, atrophies from 7 y/o onwards
- Lingual = posterior surface of tongue
Laryngopharynx
- Behind larynx
- Terminates to level of cricoid cartilage (becomes continuous w/ oesophagus)
Larynx
Cartilaginous, made of:
- Thyroid cartilage
- Cricoid cartilage
- Epiglottis
- Arytenoid cartilage
Trachea
- Begins at C6, below cricoid cartilage of larynx
- Descends through thorax
- Divides at T4 into 2 principal bronchi
- C-shaped tracheal cartilage rings, anteriorly united by fibroelastic membrane, posteriorly by trachealis muscle
- Lined w/ psuedostratified columnar epithelium with goblet cells - ciliated to transport mucus + inhaled particles of lungs - swallowed + neutralised by stomach
Corina
Thick, incomplate cartilaginous ring - runs between 2 primary bronchi at bifurcation of trachea
- Directs air into principal bronchi during respiration
- Most sensitive area of the trachea for triggering the cough reflex
Primary bronchi
- Begin at T4 - L and R bronchi emerge as division of trachea
- Similar structure to trachea - incomplete rings of cartilage anteriorly united by fibroelastic membrane
- Travel obliquely to enter each lung through hilum - divide into smaller branches
Describe the structural differences between the left and right bronchi
Left = vertical, shorter, wider
Right = horizontal, longer, narrower
Obstruction more likely in left bronchi
Secondary (lobar) bronchi
- Branches of principal bronchi
- Left = 2, Right = 3 (1 per lobe)
Tertiary (segmental) bronchi
- Each serves specific bronchopulmonary segment
- Left = 8, Right =10
- Cartilaginous plates - not c-shaped
- Branch into bronchioles
Describe the general structure of bronchioles
Composed of fibroelastic membrane and smooth muscle, usually don’t contain cartilage
Terminal bronchioles
- No cartilage
- Mostly smooth muscle
- Branch into respiratory bronchioles
Respiratory bronchioles
- Branch into alveolar ducts, have alveoli directly attached to them
Describe the location of the lungs
In the thoracic cavity, occupying most of the space around the mediastinum
Describe the structure of the lobes of the lungs
Left = 2 lobes, superior + inferior Right = 3 lobes, superior, middle and inferior
Describe the fissures of the lungs
Fissures = narrow depressions which separate the lobes
Right = oblique and horizontal fissures
Left = Oblique fissure
Describe the pulmonary circulation
2 pulmonary arteries from the heart supply the lungs (1 per lung) with deoxygenated blood and 4 pulmonary veins (2 per lung) return oxygenated blood to the heart
Describe the blood supply to the lungs
Lung tissue is supplied with oxygenated blood via the bronchial arteries - direct branch of the aorta. Bronchial veins drain deoxygenated from the lungs. Left bronchial vein drains into the hemizygous vein, right bronchial vein drains into the azygous vein.
Hilum
Triangular structure of the medial surface of the lung - primary bronchi and neurovascular structures enter and leave the lung here
List the regions of the lungs
- Apex = tip, protrudes above clavicle
- Base = inferior concave surface, rests on diaphragm
- Hilum
- Cardiac impression s = concavity on ateroinferior + medial surfaces of each lung where heart rests - larger on left lung
Describe the structure of the pleura
- Double sheet of thin serous membrane
- Each is a closed sac with the lung invaginated into it
- Creates 2 layers - continuous at the hilum
- Visceral
- Parietal
Which anatomical landmark indicates the bifurcation of the trachea into the left and right primary bronchi?
Bifurcation occurs at the level of the sternal angle
Describe the mucociliary escalator
- Trachea is lined by ciliated pseudostratified columnar epithelium
- has goblet cells which produce mucin
- Inhaled particles and pathogens become trapped in the mucus, which is swept up the airways by cilia
- Mucus and trapped particles/pathogens are then swallowed
Describe the innervation of the trachea
Sensory info from the recurrent laryngeal nerve
Describe the vascular supply to the trachea
- Arterial supply from tracheal branches of inferior thyroid artery
- Venous drainage via brachiocephalic, azygous + accessory hemizygous veins
Describe the innervation of the bronchi
Pulmonary branches of the vagus nerve (CN x)
Describe the vascular supply to the bronchi
- Arterial supply = bronchial arteries
- Venous drainage = bronchial veins
Conducting bronchioles
- Branch from tertiary bronchi
- For transport/direction of air
- Don’t have glands
- Not involved in gas exchange
Describe the innervation of the lungs
- Derived from pulmonary plexus
- Sympathetic, parasympathetic + visceral afferent fibres
Describe the parasympathetic innervation of the lungs and its effect
Derived from the vagus nerve, stimulates secretion from bronchial glands, contraction of bronchial smooth muscle + vasodilation of pulmonary vessels
Describe the sympathetic innervation of the lungs and its effect
Derived from sympathetic trunks, stimulates relaxation of bronchial smooth muscles and vasoconstriction of pulmonary vessels
Describe role of the visceral afferent innervation of the lungs
Conducts pain impulses to sensory ganglion of the vagus nerve
What are alveoli?
- Tiny-thin walled sacs with rich blood supply
- Site of gas exchange - high surface area
Describe the structure of the alveolar walls
- One cell thick, capillaries are also one cell thick (gases diffuse across 2 cells)
- Internal surface covered in alveolar fluid - allows gases to dissolve for diffusion. Contains surfactant.
- Contain macrophages that phagocytose foreign particles
- Wall composed of type I and II alveolar cells surrounded by epithelial basement membrane
Composition and function of surfactant
Rich in phospholipids and proteins that decrease surface tension in alveoli, preventing collapse of thin alveoli walls which are prone to collapse. Prevents alveoli from sticking together with each breath by keeping surface between cells and air moist.
Type I alveolar cells
- Broad, simple squamous epithelial cells
- Majority of cells lining walls of alveoli
- Function = lie in a thin, single layer which allows from diffusion of gases across respiratory membrane
Type II alveolar cells
- Cuboidal-shaped cells that line remaining space on walls of alveoli
- Fewer in number that type 1 alveolar cells
- Function = repair alveolar wall after damage + secrete surfactant.
Alveolar basement membrane
- Epithelial basement membrane, thin extracellular membrane surrounding alveolar wall
- Basal lamina + fibrous reticular lamina
- Function = anchors alveolar cells to surrounding connective tissue
Describe the function of the interstitial space
- Minute gap between cells and tissues
- Filled with interstitial fluid, bathes surrounding cells
- Function = allows diffusion of gases to occur across respiratory membrane
What is a serous membrane?
Layer of mesothelial cells, supported by connective tissue
Pleural cavity
- Potential space between 2 layers of the pleura
- Contains small volume of serous fluid
Describe the function of the fluid in the pleural cavity
- Lubricates surfaces of plurae, allowing them to slide over each other without friction
- Produces surface tension - pulling parietal + visceral pleura together - ensures that when the thorax expands the lung also expands, filling w/ air
Parietal pleura
- Covers internal surface of thoracic cavity
- Thicker than visceral pleura
Visceral pleura
- Covers outer surface of lungs
- Extends into interlobar fissures
Pleural recesses
- Anteriorly and posteroinferiorly pleural cavity is not entirely filled by lungs - produces recesses
- 2 recesses in each pleural cavity
List the pleural recesses present in each pleural cavity
- Costodiaphragmatic = between costal pleurae + diaphragmatic pleura
- Costomediastinal - between costal pleurae and mediastinal pleurae, behind sternum
Describe the neurovascular supply to the parietal pleura
- Sensitive to pressure, pain and temperature
- Produces well localised pain
- Innervated by phrenic + intercostal nerves
- Blood supply from intercostal arteries
Describe the neurovascular supply to the visceral pleura
- Not sensitive t pain, temperature or touch
- Sensory fibres only detect stretch
- Receives autonomic innervation from pulmonary plexus (sympathetic trunk + vagus nerve)
- Arterial supply via bronchial arteries (branches of descending aorta), also supply parenchyma of lungs
What is the cough reflex?
Unlearned, automatic reflex mechanism of lungs to get rid of noxious harmful substances (protective reflex) - expels foreign material from lungs
What are the requirements of the cough reflex?
- Large volume of air to clear foreign material
- Fast flow rate of air - generation of large pressure gradient between lungs + atmosphere
- A stimulus to irritate the lining of the airway - mechanical or chemical
Describe the mechanism of the cough reflex
- Rapid deep inspiration - brought about by contraction of diaphragm + external intercostal muscles
- Closure of glottis (vocal folds) - simultaneously, relaxation of inspiratroy muscles, contraction of expiratory muscles (internal intercostal + abdominal muscles)
- High intra-thoracic pressure generate - sudden opening of vocal cords, rapid expulsion of unwanted foreign material
Explain how the cough reflex is triggered
- Pulmonary irritant receptors that detect stimulus -rapidly acting pulmonary stretch receptors, found mainly in pharynx + trachea
- Afferent pathway - branches of vagus nerve -> medulla oblongata in brainstem of CNS (respiratory centre)
- Efferent pathway - several - phrenic nerves, spinal motor nerves travel to effector muscles, laryngeal muscles, abdominal muscles
Define asthma
Common chronic disease primarily affecting the small conducting airways of the lungs. Causes intermittent episodes of reversible airway obstruction - treatment = removal of trigger + treatment w/ medication. Airway inflammation, airway hypersensitivity, airway obstruction.
How does asthma cause obstruction in the airways
- Smooth muscle spasm in walls of small bronchi/bronchioles
- Oedema of mucosa of airways
- Increased mucus secretion
- Damage to epithelium
Describe the pathogenesis of obstruction due to asthma
- Mediators of inflammation (e.g. histamine, prostaglandin, leukotrienes, enzymes) - cause bronchial hyperesponsiveness + airway obstruction resulting in asthma symptoms
- Bronchoconstriction increases responsiveness of bronchial smooth muscle
- Hypersecretion of mucus - plugging of airways
- Mucosal oedema (accumulation of interstitial fluid) leading to narrowing o fairway lumen, extravasation (force fluid out) of plasma in submucosal tissues due to leakage from vessels contributes to muscosal oedema
- Infiltration of bronchial mucosa by eosinophils, masts cells, lymphoid cells + macrophages
List the classifications of asthma
- Extrinsic asthma (atopic)
2. Intrinsic asthma
Extrinsic (atopic) asthma
Early onset asthma triggered by environmental factors. Patients usually predisposed - family history of allergic diseases. IgE levels high, immediate hypersensitivity to allergen.
Intrinsic asthma
Adult onset, associated with chronic bronchitis and other asthma triggers e.g. cold, exercise. IgE level normal, no family history of allergic disorders.
List the triggers/causes of asthma
- Environmental exposure to allergen
- Viral infections
- Cold air
- Emotion
- Irritant dusts, vapour + fumes
- Genetic factors
- Drugs
- Atmospheric pollution
- Exercise
Give examples of common allergens associated with asthma
Grass pollen, domestic pets
Gives examples of viral infections associated with asthma
- Rhinovirus
- Parainfluenzal virus
Give examples of drugs which can trigger symptoms of asthma
- NSAIDs
- Beta-adrenoceptors
- Blocking agents
Give examples of pollutants in the atmosphere associated with asthma
Sulphuric dioxide, ozone
Why can exercise trigger asthma symptoms?
Due to release of histamine, prostaglandins (PGs) and leukotrienes from mast cells
List the symptoms of asthma
- Breathlessness
- Chest tightness
- Wheezing - whistling noise during breathing
- Cough
List the criteria used for diagnosis of asthma
- Presence of risk factors - family history, allergen exposure, atopic history, nasal polyps
- Recent upper respiratory tract infection
- Dyspnoea - difficult, laboured breathing, worse with allergen exposure, cold air etc.
- Cough
- Expiratory wheezes
- Nasal polyposis
- Spirometry tests
List the drugs used to treat asthma
- Short acting beta 2 agonists e.g. sulbutamol
- Long acting beta 2 agonists - salmeterol
- Antimuscarinic bronchodilators e.g. corticosteroids
Explain how corticosteroids work to treat asthma
Decrease airway inflammation (decrease oedema and mucus secretion)
List the types of inhalers used to treat asthma
- Reliever inhaler (blue)
2. Preventer inhaler (brown)
Describe the use of reliever inhalers
- SABA - quick relief
- Doesn’t decrease inflammation, (doesn’t help long term) only for quick relief of symptoms
- E.g. salbutamol
- Given to everyone with asthma
Describe the use of preventer inhalers
- Work over time to reduce inflammation + sensitivity of airways, decrease risk of attacks
- Used regularly (1/2 times daily) to control asthma
- Contains inhaled corticosteroids e.g. beclomethasone
- Used alongside LABA
Describe the use of LABAs to treat asthma
- Long acting beta 2 agonist - take longer to act, effects last up to 12 hours (2 times daily = full coverage) e.g. salmeterol
- Always taken with preventer - if alone it may allow condition to worsen while masking symptoms, increases chance of sudden asthma attack
List the stages of asthma
- Intermittent
- Mild persistant
- Moderate persistant
- Severe persistant
Intermittent asthma
- Symptoms e.g. wheezing come and go
- Symptoms < 1/2 times per week, nighttime awakening <2 per month
- No interference with normal activity/lung function
- Inhaler use < 3 days per week
- Treatment = SABA only
Mild persistant asthma
- Symptoms >2 days per week, not daily, 3-4 nighttime awakenings per month
- Inhaler use > 2 days per week, not daily, not more than 1 per day
- Minor limitation on normal activity
- Treatment = SABA, long acting steroids (blue and brown inhalers)
Moderate persistant asthma
- Daily symptoms, nighttime awakenings > 1 per week
- Daily inhaler use
- Some limitation on normal activity, decreased lung function
- Treatment = low-dose steroid, LABA
Severe persistant asthma
- Symptoms througout the day and nighttime awakening may be every night
- Attacks severely limit normal activity
- SABA required several times per day
- Lung function severely decreased
- Treatment = high does inhaled steroids, LABA
List examples of electrical signalling
- Between nerve cells
2. Stimulation of cardiac cells
Describe the movement of electrical impulses along nerve cells
When nerve is stimulated, a wave of altered charge (depolarisation, action potential) sweeps along the membrane of the nerve axon. The mechanism for charge changes = sequential opening and closing of ion channels in axon membrane.
Describe how electrical signalling stimulates cardiac cells
- In pacemaker cells - Purkinje fibres. Ion movements across membrane carry charge signals (like nerves)
- In myocytes - charge transmitted through gap junctions
Describe the mechanism by which ion-channel linked receptors allow for signalling between cells
- Receptor is an ion channel
- Binding of ligand to receptor causes conformational change that opens ion channel
- Ion moves through channel along concentration gradient - inhibits action potential formation (depolarisation)
Give an example of signalling through ion-channel linked receptors and explain its mechanism of action.
Acetylcholine at the neuromuscular junction:
- Acetylcholine released from motor neurone
- ACh binds to ion-channel receptor on muscle cell, opens sodium channel
- Sodium ion entry causes depolarisation of muscle cell membrane and muscle contraction
- Acetylcholinesterase enzyme and reuptake transporter switch off the signal
Give examples of G-protein coupled receptors
Adrenaline (hormone), serotonin (neurotransmitter)
Explain the mechanism of action of G-protein-coupled receptors
- Ligand binding to extracellular domain causes conformational change in cytoplasmic domain
- Conformational change allows G-protein to bind receptor and be activated
- Activated G-protein activates downstream enzymes
What are:
a) First messengers
b) Second messengers
a) Ligand/hormones
b) Small molecules that transduce signal from cell surface to effector proteins that produce the cell’s response e.g. cAMP, DAG
What do the following second messengers do:
a) cAMP
b) Calcium ions
c) DAG
a) Activates protein kinase A
b) Activates calcium-dependent enzymes
c) Activates protein kinase C
Explain the effects of adrenaline and the GPCRs that adrenaline binds to to elicit these cell-specific responses
- Increased heart rate/force, Beta 1 adrenergic receptors in cardiac muscle cells
- Bronchodilation, vasodilation - increased blood supply to skeletal musce, Beta 2 adrenergic receptors in airway smooth muscle lining, vascular smooth muscle cells
- Vasoconstriction - reduced blood flow, Alpha 1 adrenergic receptors in vascular smooth muscle cells
- Vasoconstriction - reduced blood flow, Alpha 2 adrenergic receptors in vascular smooth muscle cells
List the methods of drug administration through parenteral injection sites
- Subcutaneous injection
- Intramuscular injection
- Intravenous injection