2.03 - Pathology Of Pneumonia Flashcards
Describe the histology of the Trachea
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
Describe the histology of a bronchus
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
Describe the histology of a bronchiole
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
How does a respiratory bronchiole differ from a terminal bronchiole?
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
What are the types of cells in an alveoli?
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
What is the function of acute inflammation?
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
How can pneumonia be classified?
Causative agent
Clinical setting (e.g. community acquired, hospital acquired)
Mechanism (e.g. aspiration)
Gross anatomic distribution (bronchogenic, lobar)
Describe bronchopneumonia
Patchy consolidation of the lung
Extension of a preexisting bronchitis
Common at the extremes of life
Describe lobar pneumonia
Acute infection of an entire lobe (bacterial, tissue consolidation and then leakage of fluid into tissues)
Onset abrupt
Now infrequent due to antibiotic treatment
What are the four stages of lobar pneumonia?
Congestion
Red Hepatisation
Grey Hepatisation
Resolution
Describe the congestion phase of lobar pneumonia
Enlarged lobe Heavy Capillaries dilated and congested with blood Air spaces filled with pale fluid Occasional bacteria
Describe the red hepatisation phase of lobar pneumonia
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
Describe the grey hepatisation phase of lobar pneumonia
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
Describe the resolution phase of lobar pneumonia
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
What are the others types (beside bacterial) of pneumonia?
Viral (respiratory syncytial virus, cytomegalovirus)
Fungal (pneumocystis)
Aspiration
Lipid
Describe the pneumonia caused by respiratory syncytial virus
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
Describe the pneumonia caused by cytomegalovirus
Herpes virus Newborns and immunocompromised Transplant recipients Chronic interstitial pneumonitis Classic intra-nuclear and cytoplasmic inclusions
Describe aspiration pneumonia
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
Describe lipid pneumonia
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
What are some complications of bacterial pneumonia (lobar and broncho)
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
What are some signs and symptoms of bacterial pneumonia?
Fever Cough Sputum Pleuritic chest pain Increased respiratory rate Cyanosis Leukocytosis
