Asthma Flashcards
Give a brief overview of airway changes seen in asthma
- Infiltration of inflammatory cells
- Hypertrophied smooth muscle (remodelling)
- Oedema
- Mucus plug
- Thickened basement membrane
What are the symptoms for asthma? And what are it’s triggers?
Recurrent wheeze and breathlessness caused by reversible airways obstruction due to complex chronic inflammation of bronchial exposure.
Asthma has multiple triggers: Allergy, infection, cold, exertion, irritation, drugs, occupational exposure.
How can asthma be classified?
- Allergen-induced:
- e.g. house dust mite, pollen, ragweed, cockroach, mold
- Non-allergen induced
- Ozone, cigarette smoke, diesel particles, infection, aspirin, exercise, cold air
- Intrinsic asthma
- based on inherited genes
What’s the hygeine hypothesis?
Those people brought up in developing countries who have been exposed to more bacteria due to: poor sanitation, rural living, low antibiotic use, larger families etc have a lower chance of developing allergies compared to those brought up in westernised countries.
What are the chances of developing asthma if either one of the parents has it, or both of them?
A child who has an asthmatic parent is 3-6 times more likely to develop asthma compared to a person with two normal parents.
Whereas a person with two asthmatic parents is 10 times more likely to develop asthma compared with a child with two normal parents.
The gene ADAM 33 predisposes someone to developing asthma.
What does this gene do?
- Promotes smooth muscle cell proliferation
- Promotes mesenchymal cell proliferation
- And it also causes the release of cytokines to attact inflammatory cells
- And it causes myofibroblasts and fibroclasts to produce collagen which causes permanent changes in the airway.
Why does the airway get obstructed is asthma?
Bronchoconstrictin
Bronchial wall inflammation
Hypersectretion of mucus
What are the pathophysiological features of asthma?
- Airways get inflammed
- There’s bronchial over-responsivenss
- Bronchoconstriction
- Bronchial wall edema
- Excess mucous secretion
- Epithelial shedding
- Airway remodeling
What are the two classes of immune responses to asthma?
Early phase response: Involves type I hypersensitivity, with allergens crosslinking IgE receptors on Mast cells.
Late phase response: Involves type IV hypersensitivity, T cell mediated response activates eosinophils, B cells, others lead to airway remodling
Describe the later phase response to asthma
The allergen moves through the mucosa and is uptaken by an APC, and is then presented to a Th2 cell. This is activated, and it releases IL-4 which causes B cells to class switch to IgE antibodies, and also relases IL-3, 5 to activate eosinophils which release their granules.
The IgE binds to IgE Fc receptor on the surface of mast cell (this can now participate in type I hypersensitivity).
And granules released by eosinophils causes: an infiltration of leukocytes, mucus secretion, epithelial damage, bronchospasm, mucosal oedema
How does the bronchospams
Antigens excite the vagal autonomic pathway, precipitating the bronchospasm
Bronchocontstriction and mucous secretion are due to increased PNS activity
What are the histological changes seen in the mucosa in asthma?
Theres an increase in the number of goblet cells (For increased secretion), and theres a thickened basement membrane, and more smooth muscle (due to smooth muscle cell proliferation)
*May be missing key points but just want she said
What are Curschmann’s spirals?
They are spirals of mucous, which contrain shed epithelial cells
These are found in the sputum of asthmatics
What changes are seen in the airway remodelling in asthma
- Inflammation causes thickening of the basement membrane
- There is mucus hypersecretion (gland hyperplasia)
- Suberepithelial fibrosis (due to collagen production)
- There’s airway smooth muscle hypertrophy (Smooth muscle cell proliferation)
- Angiogenesis
What can exacerbate asthma?
- Poorly controllled airway inflammation
- Cold air
- Viral infection
- Tabacco smoke
- Environmental allergens indoor or outdoor
What is occupational asthma, and how is it caused
it’s asthma associated with work exposure. It involves sensitisers and irritants.
Occupational asthma can either be sensitizer induced, or irritant induced.
Sensitizer induced asthma is asthma in response to a specific antigen, and once the person is sensitised then only low levels are required to cause an asthmatic response (sterotyped response). Person will have to leave job (medical removal).
In irritant induced asthma, it can be caused by moderate to heavy exposure to any irritant. The response may not be sterotyped, and may be variable - may not have to leave the job in medical removal, often last resort.
