PBL 3 - smoking, COPD etc Flashcards
what does COPD stand for?
chronic obstructive pulmonary disease
what does COPD consist of?
chronic bronchitis + emphysema
what is the definition of COPD?
a disease state characterised by airflow limitation that is not fully reversible
what is chronic bronchitis?
long-term inflammation of the mucous membranes of the bronchi
what are causes of chronic bronchitis?
- caused almost entirely by smoking
- infection — viral, bacterial
- air pollution — smog
- occupational exposure
bronchitis effects on bronchi and mucus
- immobilisation and damage to cilia (due to cigarette smoke)
- enlargement of mucus secreting glands in the trachea and bronchi, leading to hypersecretion of mucus
- bronchial mucosal inflammation
- progressive airflow limitation
what is the effect of paralysed cilia on mucus?
mucus gets stuck
name 4 structural histological changes in chronic bronchitis
- much more mucus glands in smoker = more mucus
- fibrous tissue
- inflammation
- smooth muscle cell hypertrophy
how does mucus build up cause inflammation?
mucus that airway hasn’t been able to shift collects bacteria — more inflammation
how does fibrous tissue affect the airways?
makes the airway rigid — failure to get rid of mucus by coughing — remodelling of airway — airways less able to contract and expand
pathogenesis of chronic bronchitis
- primary or initiating factor is the long-standing irritation by inhaled substances (eg. tobacco smoke)
- initially, proteases released from neutrophils stimulate mucus hypersecretion in the large airways
- results in hypertrophy of the submucosal glands in the trachea and bronchi
- increase in goblet cells of small airways leads to excess mucus production — contributes to airway obstruction
- it is thought that both the submucosal gland hypertrophy and the increase in goblet cells are protective meta plastic reactions against tobacco smoke or other pollutants
what is emphysema?
long term, progressive disease of the lungs in which there is loss of alveolar walls, reducing SA for exchange of gases
what are alveolar walls and their elasticity critical for?
the retention or potency of small airways
why is emphysema an obstructive lung disease?
because airflow on exhalation is slowed or stopped
what is responsible for opening up air spaces in inhalation?
elasticity of the alveolar walls
how does emphysema affect the opening and closing of air spaces?
it is reduced because emphysema destroys the alveolar walls so the airway opening by pull of elasticity is reduced
what are the 2 main types of emphysema?
centriacinar (centrilobular) and panacinar (panlobular)
what is the main difference between the 2 types of emphysema?
- centrilobular is associated with smoking (more common)
- panlobular is inherited
what do tobacco products release from white cells and what is the effect?
- release inflammatory products from white cells, mainly neutrophil polymorphs
- these inflammatory products break down elastic tissue
what does tobacco products inhibit?
a-1-antitrypsin therefore more elastase activity breaking down air space walls
what does circulating a-1-antitrypsin usually do?
has anti-elastase activity (elastase breaks down alveolar walls)
what happens to the size of airspaces in emphysema compared to a normal lung?
airspaces on average are 2x the diameter of a normal lung
if the diameter of air spaces 2x normal, what is the effect on oxygen transfer?
decreases area of wall available for oxygen transfer = 16x less (2^3)
what is pulmonary fibrosis?
excess deposition of collagen and other extracellular matrix components in the lungs = “scarring of the lung”