2.03 - Pathology Of Pneumonia

Question 1

Describe the histology of the Trachea

Answer 1

Lumen
Mucosa - Epithelial layer: Pseudostratified ciliated columnar epithelium and also goblet cells (get fewer and fewer as move down respiratory tract)
Submucosa –> seromucus layer
Tracheal cartilage layer –? hyaline cartilage, 12-14 cartilage rings important in maintaining the structure
Adventitia

Question 2

Describe the histology of a bronchus

Answer 2

Mucosa- epithelial layer (ciliated pseudostratified columnar epithelium with goblet cells), lamina propria
Discontinuous smooth muscle layer (becomes more prominent at bronchioles)
Submucosa- seromucinous glands
Discontinuous plates of cartilage

Question 3

Describe the histology of a bronchiole

Answer 3

Mucosa - Epithelial layer (ciliated columnar/cuboidal epithelial cells as well as non-ciliated Clara cells)
Smooth muscle layer prominent
Lost cartilage layer
Adventitia- fuses with surrounding tissues helping to keep all structures in the respiratory tree in place

Question 4

How does a respiratory bronchiole differ from a terminal bronchiole?

Answer 4

Terminal bronchioles purpose is to allow passage of air, so not gas transfer takes place. Respiratory bronchioles often have alveoli coming of their walls so can aide in gas transfer

Question 5

What are the types of cells in an alveoli?

Answer 5

Type 1 pneumocyte - gas exchange
Type 2 pneumocyte - secrete surfactant
Alveolar macrophages - within alveolus, usually can see material in cytoplasm
Also, between alveoli are pores that help to keep them open if bronchiole is blocked, physical benefit and supplies collateral airflow from alveolus next door

Question 6

What is the function of acute inflammation?

Answer 6

Fluid dilutes toxins
Fibrinogen converted fibrin
o Immobilises infectious organisms
o Scaffolding for the migration of neutrophils
Immunoglobulins may neutralize infectious organisms
Neutrophils
o Phagocytoseandkillorganisms
o Secrete enzymes initiating lysis of dead cells

Question 7

How can pneumonia be classified?

Answer 7

Causative agent
Clinical setting (e.g. community acquired, hospital acquired)
Mechanism (e.g. aspiration)
Gross anatomic distribution (bronchogenic, lobar)

Question 8

Describe bronchopneumonia

Answer 8

Patchy consolidation of the lung
Extension of a preexisting bronchitis
Common at the extremes of life

Question 9

Describe lobar pneumonia

Answer 9

Acute infection of an entire lobe (bacterial, tissue consolidation and then leakage of fluid into tissues)
Onset abrupt
Now infrequent due to antibiotic treatment

Question 10

What are the four stages of lobar pneumonia?

Answer 10

Congestion
Red Hepatisation
Grey Hepatisation
Resolution

Question 11

Describe the congestion phase of lobar pneumonia

Answer 11

Enlarged lobe
Heavy
Capillaries dilated and congested with blood
Air spaces filled with pale fluid
Occasional bacteria

Question 12

Describe the red hepatisation phase of lobar pneumonia

Answer 12

Looks solid and not sponge like, very vascular and dilated
Cut surface is dry and red, resembles liver
Increased numbers of neutrophils
Fluid which contained fibrinogen has clotted in the alveolar spaces
Bacteria is more numerous

Question 13

Describe the grey hepatisation phase of lobar pneumonia

Answer 13

Still looks solid due to inflammatory exudate
Several days into inflammation, loss of the red colour after 2-3 days
Starts at hilum and moves out
Vascular response decreasing, migration of large numbers of neutrophils
Decrease in capillary congestion
Decreased blood flow through the unventilated lobe

Question 14

Describe the resolution phase of lobar pneumonia

Answer 14

Bacteria/inflammatoryexudatedigestedby enzymes and return to structure there before
Liquefaction of the previously solid exudate
Fibrinolytic enzymes
Apoptosis of neutrophils
Fluid contents removed
Takes several weeks

Question 15

What are the others types (beside bacterial) of pneumonia?

Answer 15

Viral (respiratory syncytial virus, cytomegalovirus)
Fungal (pneumocystis)
Aspiration
Lipid

Question 16

Describe the pneumonia caused by respiratory syncytial virus

Answer 16

Winter epidemics
Children under 6 months particular prone URT –> LRT
Bronchilotis and pneumonia
Destrution of bronchiolar epithelium
Epithelium debris, mucus plugs and fibrin
Giant cells

Question 17

Describe the pneumonia caused by cytomegalovirus

Answer 17

Herpes virus
Newborns and immunocompromised
Transplant recipients
Chronic interstitial pneumonitis
Classic intra-nuclear and cytoplasmic inclusions

Question 18

Describe aspiration pneumonia

Answer 18

Aspiration pneumonia favoured by
Loss of consciousness
Suppression of cough reflex 
Dysphagia
Poor oral hygiene

Affects dependent parts of the lung
Apical lower lobe
Basal upper lobe

Bronchopneumonia pattern

Bacteria responsible are the flora of the URT
Florid peri-bronchial consolidation
Necrosis
Particles of undigested food present
Foreign body giant cells

Question 19

Describe lipid pneumonia

Answer 19

Lung generates lipid within surfactant (decreases alveolar surface tension)
Surfactant cleared by alveolar epithelium and via the airways
Obstruction (foreign bodies, tumour) of airways leads to build up of lipid in macrophages

Question 20

What are some complications of bacterial pneumonia (lobar and broncho)

Answer 20

Broncho pneumonia
o Healing by fibrosis
o Abscess formation

Lobar pneumonia
o Pleuritis
o Empyema (build up of pus in pleural cavity) 
o Abscess formation
o Haemotogenous seeding
o Death

Question 21

What are some signs and symptoms of bacterial pneumonia?

Answer 21

Fever
Cough
Sputum
Pleuritic chest pain
Increased respiratory rate
Cyanosis
Leukocytosis