Lecture 2: The pathology of Asthma Flashcards
What is the pathogenesis of asthma?
Cough, wheeze or chest tightness at night or in the morning after exposure to a variety of environmental stimuli.
What are the airways of asthmatic patients like?
Hyper-responsive to the constrictor effects of a number of stimuli
What are the specific stimuli that trigger asthma?
- Aspirin
- allergens
What are the non specific stimuli that trigger asthma?
- Exercise
- Cold air
- Hyperventilation
- Chemical agents
How does cold air breathing lead to asthma through heat loss?
- Breathe cold air
- Heat loss
- Mucosal cooling
- Sensorineural activation
- Changes in epithelial ion transport
- Increased blood flow
- Venous ebgorgement
- Increased glandular activity
What are the characteristics of asthma?
- Inflammatory cells involved are eosinophils, mast cells and neutrophils
- Smooth muscle is hyper responsive to substances that cause contraction such as acetylcholine, histamine and PAF
- Smooth muscle is hypresponsibe to substances that cause relaxation such as adrenaline
- Neuronal imbalance - increase in parasympathetic activity and decreased sympathetic activity
- Remodelling of airways - hyperplasia and hypertrophy
What is the predominant cell in asthmas?
Eosinophil
What does the inflammatory response result in?
- Causes the release of inflammatory mediators
- They can activate sensory C fibres in the epithelial layer of the airway
- This can cause a reflex bronchoconstriction, making it difficult for the patient to breathe
What is acetylecholine released by?
Parasympathetic nerve
What causes bronchoconstriction in the airway?
- Acetylecholine
- Histamine
- Platelet aggregating factor
What substances are smooth muscles hyperresponsive too?
- Aceytlecholine
- Histamine
- Platelet agregating factor
What substances are smooth muscles hyporresponsive too?
Adrenaline
What causes relaxation of smooth muscles?
Adrenaline
What are the three major nerve control mechanisms in the airway?
- Parasympathetic nerve releases acetylecholine to cause bronchoconstriction
- Adrenergic nerves releases noradrenaline - this inhibits the release of acetylecholine from the parasympathetic nerve so causes bronchodilation
- Non adrenergic nerves: actiavted in the epithelium through C fibre stimulation by inflammatory mediators - they can cause excitary and inhibitory responses (bronchodilation and bronchoconstriction)
What is hyperplasia?
Cells divide causes engorgement of tissue
What is hypertrophy?
Increase and growth of cells
What are the changes in the airways in an asthmatic patient?
- Layer of the smooth muscle contracts causing bronchoconstriction - narrowing of airway lumen
- Damage, hypertrophy swelling of epithelial lining
- Enhanced activity of goblet cells - secrete mucus in response to inflammation
What is mucosal odema?
Formation of mucus plug in the airway
What is the basement membrane?
The layer upon which the epithelial cells sit
What are the morphological changes in bronchitial asthma?
- Lungs are over distended due to over inflamation
- Small areas of atelectasis (lung collapse) can be seen
- Occlusion of bronchi and bronchioles by thick tenacious mucous plug