Obstructive lung disease Flashcards
What is the function of the clara cells/club cells?
1) They form the defensive Clara cell secretory proteins
2) Repairs ciliated and secretory cells
3) Metabolizes xenobiotic compounds
How can infections travel from one alveoli into another?
Through the pores of Kohn, which are perforations in the wall of the alveoli
What is the importance of the surfactant?
- Made of lecithin (lipid) secreted by type-2 alveolar cells
The alveoli are soaked in blood, and thus the surfactant will reduce the surface tension created by the extravasation of blood
What are the two main functions of the respiratory system?
1) Ventilation (depends on the respiratory center, neural tracts, & respiratory muscles)
2) Perfusion (depends on the equal distribution of blood and air in the lungs)
what happens in case of hypoventilation and what are its main causes?
- Hypoxia + hypercapnia
1) Obstructive Hypoventilation
2) Restrictive hypoventilation
What are the causes of obstructive hypoventilation?
1) Upper airway obstruction
- Like laryngeal edema
2) Lower airway obstruction
- COPD
- Bronchial asthma
- Bronchiectasis
What are the causes of restrictive hypoventilation?
- The alveoli lose the capability of expanding and recoiling due to:
1) Decreased compliance of:
- Lungs
- Pleura (pneumothorax, or fluid)
- Chest wall (in extreme obesity)
2) Disorders of the neuromuscular apparatus
Why do we not feel dyspnea in hypoventilation?
Due to the accumulation of CO2 which will depress the respiratory centers
How can lung perfusion be affected?
- Impaired perfusion = hypoxia + normo and sometimes hypocapnia (so patient will present with dyspnea)
1) Emphysema
2) Pulmonary edema
3) Pneumonia
4) Interstitial lung disease
What is meant by diffuse lung disease?
Lung diseases the affect the whole lung
What are the types of diffuse lung disease?
1) Obstructive lung disease
2) Restrictive lung disease
What is meant by obstructive lung disease?
It is characterized by the reduction of airflow, causing shortness of breath in exhaling air, due to increased resistance and thus it will decrease the FEV1 and FVC, increasing the total lung capacity and residual volume
What are some examples of obstructive lung diseases?
1) COPD (Emphysema, Chronic bronchitis)
2) Bronchial asthma
3) Bronchiectasis
What is meant by chronic emphysema?
It is a chronic lung disease that is characterized by abnormal, irreversible dilatation of the airspace distal to the terminal bronchiole, there is wall destruction but no fibrosis
What are the types of emphysema?
- According to the location within the lobule:
1) Centriacinar (dilatation of the central part of the respiratory bronchiole), common in the upper lobes of smokers
2) Panacinar (all airspace beyond the terminal bronchiole are dilated, more common in the lowe lobes, associated with a1-anti-trypsin-deficiency)
3) Paraseptal (distal acinar, affecting distal airspace at the periphery, adjacent to the pleura and more in the upper respiratory lobes)
4) Irregular (scar emphysema, occurring near healed inflammatory process like TB scars)
What are the causes of emphysema?
1) Environmental factors
- cycles of inflammation and proteolysis of the ECM (due to the exposure of the epithelium to toxic substances like cigarette smoke)
- Defective in anti-inflammatory mechanism
- Airway infection
2) Genetic factors
- Deficiency of a1-antitrypsin (PiZZ gene causing the misfolding of protein preventing it from being secreted into the blood, increasing inflammation leading to liver cirrhosis)
- Polymorphism of the TGF-b gene, causing an inadequate synthesis of ECM
Describe the morphology of emphysema
1) Gross
- Affects the upper 2/3 of the respiratory system
- Bullae/blisters in irregular and distal acinar emphysema
2) Microscopically
- Abnormally large alveoli separated by thin septa
- The number of alveoli capillary is diminished
- The terminal and respiratory bronchioles are diminished
- No interstitial fibrosis
What are the complications of emphysema?
1) Pulmonary hypertension
2) Hypoxia (due to decreased number of pulmonary caps, hypoventilation, expansion of the alveolar wall)
3) Reduction in the pulmonary vascular beds
4) Lung collapse, if the bullae rupture into the pleural space
What is the meaning of chronic bronchitis?
Its clinical definition is persistent cough + sputum production for 3 months at least for 2 consecutive years
What are the causes of chronic bronchitis?
1) Cigarretes (90% of patients are smokers)
2) Air pollutants (like nitrogen dioxide)
3) Toxic inhalants
4) Infection (S.pneumonia, H.influenza)
Describe the pathogenesis of chronic bronchitis
1) The irritants will cause hypersecretion of mucus, which will lead to the hypertrophy of the submucosal glands in the trachea and bronchi thickening the alveoli and narrowing the lumen, and hyperplasia of goblet cells “metaplasia in small bronchi”
2) The irritants will also lead to inflammation which will lead to the infiltration of the alveoli by the CD8 lymphocytes (releases IL-13), macrophages (releases metalloproteinases), and neutrophils (releases elastase)
3) Cigarette smoke will damage the airway epithelium, increase the production of mucin, and elastoproteases from the neutrophils
What are the types of chronic bronchitis?
1) Simple chronic bronchitis (white sputum)
2) Chronic mucopurulent bronchitis (yellow sputum)
3) Chronic asthmatic bronchitis (intermittent bronchospasm and wheezing)
4) chronic obstructive bronchitis (chronic irreversible airway obstruction)
Describe the morphology of chronic bronchitis
1) Gross: 1. Thickened bronchial wall, 2. Hyperemia and swelling of the mucous membrane, 3. mucus in the lumen
2) Microscopy:
- Hypertrophy of the mucus-secreting glands measured by the Reid index, which measures the distance from the epithelial wall to the cartilage >0.4 = chronic bronchitis
- Mixed inflammatory cells
- Increased amount of goblet cells in the surface epithelium
- Chronic bronchiolitis, when the inflammation affects small airways
What are the clinical features of chronic bronchitis?
- Blue Bloaters
- Hypoxemia (central cyanosis)
- Pulmonary hypertension
- Hypercapnia (no dyspnea)