Airways

Question 1

Describe normal lung histology

Answer 1

The normal lung is characterised by thin septae, lined with type I pneumocytes. Contained within these septae are thin-walled capillaries, optimised for gas exchange.
The alveoli are uniformly arranged, and are empty.
Arteries and bronchi/bronchioles are accompanied together.
Veins and lymph vessels are accompanied together.
Note also that type II pneumocytes, while present, should not be visible in normal lung histology.

Note that while trachea and bronchus have:
- pseudostratified columnar ciliated epithelium
- submucosa - with minor salivary glands, key for lubrication
- cartilage
Bronchioles have no cartilage as there is no need for that additional support distally.

Question 2

Describe a systematic approach to medical lung diseases

Answer 2

• alveolar space is usually empty. If NOT, this indicates pathology. Featuers include macros, neutros, fluid, pus and inflammatory cells
  
  • alveolar septa are typically empty. If NOT, this indicates pathology. Features include: inflammation, oedema, fibrosis and scarring
    Both can hamper O2 exchange

Question 3

HI

Describe the health consequences of asbestos exposure

Answer 3

Asbestos
Asbestos exposure has been associated with a number of
pathologic changes in the lungs and pleura, as listed
below:
1. Interstitial fibrosis
2. Benign serous pleural effusion
3. Bronchogenic carcinoma
4. Malignant mesothelioma
5. **Fibrous plaques of the parietal pleura

Different types of asbestos bodies: straighter fibres long deeper and predispose to mesothelioma nd lung cancer

appear as ferruginous bodies due to attraction of macrophages with ferritin and Fe-prot. complexes

Question 4

Describe etiology of emphysema

Answer 4

Emphysema is a condition of the lung characterized by irreversible enlargement of the
airspaces distal to the terminal bronchiole, accompanied by destruction of their walls without obvious fibrosis.

While septae are still thin, they have lost elasticity. Thus alveolar spaces have enlarged.
Appear as cystic spaces accompanied with some fibrosis.
Addionally septa can rupture, forming bullae or blebs.

Emphysema and chronic bronchitis are often
clinically grouped together and referred to as
chronic obstructive pulmonary disease.

Types of Emphysema include: Centriacinar, Panacinar,
Paraseptal, and Irregular

Question 5

Describe the health consequences of smoking

Answer 5

• in smokers lung, alveolar spaces are filled with macrophages and giant cells containing black carbon particles
• disease progresses from a disease of the alveolar space to septum
• if prolonged can result in fibrosis
  Damage is irreversible, can lead to dyspnoea and respiratory failure.

Question 6

Describe pathology of acute pneumonia

Answer 6

• in acute pneumonia, alveolar spaces are filled with neutrophils
• some oedema
• at later stages and/or as treatment is administered, macrophages and lymphocytes infiltrate the tissue
• fibrosis will occur if repair is hampered

Question 7

Describe pathology of alveolar proteinosis

Answer 7

• spaces contain amorphous protein like precipiate
• granular texture
• an immune condition

Question 8

Describe pathology of interstitial disease

Answer 8

• from stage 1 to 2, interstitium becomes more thick, and alveolar spaces become fewer and smaller
• stage 1 appears ‘patchy’ while stage 2 is widespread, and characterised by the presence of ‘blue’ i.e. inflammatory cells
• this is usually seen in restrictive lung diseases e.g. pulmonary fibrosis

Note that if pulmonary fibrosis/disease progresses, the lung essentially is unrecognisable and has a ‘honeycomb’ appearance, lined by hyperplastic cuboidal type II pneumocytes. These cells can be single or multinucleated and take on a ‘giant cell’ morphology.
Alveoli are much smaller.