Physiology and function in obstructive lung disease Flashcards
What is an obstructive disorder?
- Narrowing of airway (increased resistance)
- Reduced inflow of gas
- Reduced inflation of alveolus
Examples of obstructive lung diseases
- Asthma
- Chronic Obstructive Pulmonary Disease (COPD)
- Causing obstructive picture (Bronchiectasis, cystic fibrosis)
What are the factors affecting airway internal diameter?
- Increased mucus production
- Anatomical features
- Autonomic and Non-Adrenergic/ Non-Cholinergic (NANC) systems
- Inflammation
What does the airway surface liquid layer compromise of?
mucus layer (comprised of gel-forming mucins, MUC5AC and MUC5B) and the PCL (liquid filled domain), from fixed human bronchial
epithelial
PCL within cilia (low-viscosity periciliary gel layer)
How does mucous clearance occur?
The airways are covered by a layer of fluid and mucus that is constantly being propelled by cilia from the distal to proximal lung airways
The viscoelastic mucus layer is composed of secreted mucus glycoproteins (termed mucins) in addition to several secreted products.
What are the differences between large and small airways?
Larger: contain cartilage, relatively rigid
Smaller: no cartilage, susceptible to collapse
What are bronchioles?
Bronchioles are small airways, up to 1 or 2 mm in diameter, without cartilage or submucosal glands
respiratory bronchioles are distinguished from the terminal bronchioles by the alveolar sacs in their walls.
How do autonomic nervous systems interact with airway smooth muscle?
Parasympathetic vagus nerve- Acetyl choline- M3 muscarinic receptor= constriction of airway smooth muscle
Antigen in circulation- ACh- beta 2 adrenergic receptors= dilation
How do NANC NS interact with airway smooth muscle?
VIP and NO= bronchodilation
substance P and neurokinins= bronchoconstriction
How are asthma and COPD different in host factors?
A: Atopy, Sex, Low birth weight
COPD: Alpha-1 antitrypsin deficiency, low birth weight, family history, genetic predisposition
How are asthma and COPD different in environmental factors?
A: allergen exposure, occupational sensitizers, respiratory infections
COPD: smoking, occupational exposure, pollution, low SES status
How are asthma and COPD different in mechanism?
A: mast cells degranulate to release histamine leukotrienes and prostaglandins for bronchoconstriction of smooth muscle, inflammation (eosinophils) and antibody production (chemokines and interleukins= B cells)
COPD: mucous hyper secretion (macrophage chemokines, monocytes, neutrophil proteases), alveolar wall destruction (macrophage proteases, T cells), fibrosis (TGF beta and fibroblasts)
What are the reasons for airway narrowing in asthma?
- Smooth muscle thickening
- Bronchoconstriction
- Basement membrane thickening
- Mucous plugging
What happens in COPD?
- Increased mucous production
- Destruction of alveoli and connective tissue leading to collapse of conducting airways
What is Cystic Fibrosis?
CF is an autosomal recessive genetic disease. CFTR encodes its protein, a chloride and bicarbonate ion channel present on cell membranes. It is a multi-system disease affecting the GI tract, liver, reproductive system, but death is principally related to airways inflammation and infection leading to respiratory failure, which occurs from childhood. Whilst median predicted survival is 47 years of age, the median age of death in 2017 was only 31.
