Pneumonia

Question 1

Describe the detailed histological structure of the airways

Answer 1

Upper airways are lined with pseudo stratified ciliated columnar epithelium with mucus secreting goblet cells.
The epithelium sit on a basement membrane, above the lamina propia.
A band of fibroelastic tissue is beneath this. Gradually becomes more muscular throughout the airways, as it replaces the cartilage.
Submucosa: Seromucus glands, smooth muscle/elastin fibres
Cartilage: Hyaline cartilage. C-shaped and becomes less prominent as the tubes become smaller.
* Goblet cells are replaced by Klub cells in the terminal bronchioles

Question 2

Outline the differences between the different parts of the airway

Answer 2

As the airways progress towards the gas exchange regions the amount of cartilage decreases, the amount of smooth muscle increases, fewer mucus glands are seen.

Question 3

Describe the structure of the alveoli and the air-blood interface.

Answer 3

Type I pneumocytes:
Flattened, squamous epithelium with very thin cytoplasm. Allow for maximum gas exchange. Basement membrane is fused with capillary basement membrane.
Type II pneumocytes:
Rounded cells with prominent granules for production and secretion of surfactant.

Question 4

Describe the structure of the lung interstitium.

Answer 4

Contains:
Macrophages (dust cells)
Fibroblasts
Connective tissue
- A collection of support tissues. Perivascular and perilymphatic tissues, basement membrane of the alveoli and capillaries.
- Functions: Support the lung, fluid balance, repair and remodelling

Question 5

Describe the defence mechanisms employed by the respiratory system to protect the lungs from infection.

Answer 5

Coughing, sneezing, mucociliary action, cytokines, cellular immunity, IgA, IgM/G,

Question 6

Describe the aetiology of Pneumonia

Answer 6

Infection of the lungs leading to inflammation of the lungs. Mucus accumulates within the lung and consolidates. Inflammation of the alveolar septum is seen.
Can be caused by bacteria (S. pneuoniae, haemophilius influenza) , virus, fungi, mycobacteria (mycobacterium tuberculosis)
Aspiration, inhalation of the organism, infection from systemic circulation.

Question 7

Describe the types of Pneumonia

- Determined by

Answer 7

• Anatomical position, clinical setting, microbiological agent
  1. ) Lobar pneumonia: Organism spreads alveoli-alveoli. Consolidation of a lobe seen.
  2. ) Bronchopneumonia: Spreads bronchi-alveoli. Foci seen initially but can result with consolidation of the whole lobe. Young/elderly/immobile
  3. ) Immunocompromised pneumonia: E.g. cancer patients. Opportunistic infection.
  4. ) Aspiration pneumonia: Aspiration of gastric contents due to abnormal gag/swallow reflex e.g. stroke. Can be resultant of irritation by gastric contents and bacteria. Often necrotising, frequent cause of death.

Question 8

Describe the pathogenic features of Pneumonia

Answer 8

Symptoms: Fever, chills, dyspnoea, cough with purulent sputum, crackles on auscultation, consolidation on radiograph.
Diagnosis: Sputum, X-ray, FBC

Question 9

Describe the outcomes of Pneumonia

Answer 9

Treatment: Antibiotic
Death
Resolution: Destruction of connective tissue/vasculature minimal/absent.
Organization: Scar tissue, fibrosis from destruction of connective tissue. Possible bronchiectasis.
Abscess formation:
Empyema:
Bacteremia: Meningitis, arthritis, infective endocarditis

Question 10

Describe the pathological features of bronchiectasis

Answer 10

Permanent of main bronchi or bronchioles.
Consequential of pulmonary and fibrosis due to infection, bronchial obstruction or lung fibrosis.
Airways dilate as surrounding scar tissue (fibrosis) contracts.

Question 11

Describe the pathogenesis of bronchiectasis

Answer 11

Secondary to primary obstructive disease or recurrent necrotising infections.
Obstruction –> Clearance mechanism blocked –> Infection
Infection –> Damage to walls –> Weakened walls –> Dilation
Clubbing
Damage to epithelium causes bleeding
1.) Interference with drainage of bronchial secretions:
Obstruction of the airway, altered viscosity of the mucus, immotile cilia syndrome
2.) Recurrent and persistent infection weakening bronchial walls:
Predisposed to due to retention of secretions, immunodeficiency status
3.) Idiopathic bronchiectasis: In many adults no cause can be found

Question 12

Describe the effects of bronchiectasis

- Symptoms

Answer 12

Symptoms: Chronic cough, dyspnoea, production of foul smelling sputum, haemoptysis,

Question 13

Describe the pathology of the pleura

- Pleurisy

Answer 13

Infection: Pleurisy - Sharp pain on breathing deeply, coughing/sneezing, dry sound on auscultation
- Causes: Pneumonia (exudate), cancer (exudate), congestive heart failure, kidney disease, liver disease (fluid overload)
Effusion: Transudate (normal fluid) or exudate (inflammation present).
- Treatment: Antibiotics or drain

Question 14

Airway structure: Trachea

Answer 14

C-shaped rings of cartilage
Psuedostratified ciliated columnar epithelium
Mucous glands
Trachealis muscle (fibroelastic tissue) - controls diameter

Question 15

Airway structure: Bronchi

Answer 15

Discontinuous cartilage
Greater amount of smooth muscle
Mucous glands seen

Question 16

Airway structure: Bronchioles

Generally: Less cartilage, more smooth muscle, fewer glands, flatter cells

Answer 16

No cartilage
No submucosal mucous glands
No goblet cells
Klub cells secrete proteinaceous fluid
Ciliated epithelium
Terminal = Last conducting airway
Respiratory = Cuboidal ciliated epithelium and lots of openings into alveoli

Question 17

Airway structure: Alveolar Duct

Answer 17

Flat epithelium. No glands. No cilia

Question 18

Airway structure: Alveoli

Answer 18

Type I and II pneumocytes

Question 19

Airway system order

Answer 19

Trachea, left and right bronchi, 2 left and 3 right lobar bronchi, segmental bronchi, terminal bronchioles, respiratory bronchioles, alveolar duct, alveolar sac, alveolus
(From respiratory bronchiole termed the acinus)

Question 20

Epithelium - Cells of the pseudo stratified columnar ciliated epithelium

Answer 20

• Cilia: Beat rhythmically
• Basal cells: Stem cells
• Goblet cells: Produce mucus
• Neuroendocrine cells
• Klub cells: Terminal bronchioles only

Question 21

Lining of the pleural cavity

Answer 21

Visceral and parietal pleura are lined by flattened epithelium-mesothelial cells

Question 22

Describe the pathology of the pleura

- Cancer of the pleura

Answer 22

Tumour: Pleural effusion. Can be due to local tumour invasion or metastases.
- Malignant mesothelioma: Tumour of the pleura are rare.
Associated with asbestos exposure. Long latent period > 25 years. Pleural effusion also seen, exudate.