Pathology of Pneumonia: Part 1 - pathological features Flashcards
acute pneumonia
what is acute pneumonia?
inflammatory reaction of the alveoli and interstitium of the lung, usually caused by infectious agents
what is exudate
fluid leaking from nearby blood vessels containing protein and other materials
what are 2 characteristics of acute pneumonia?
- Inflammatory exudate in alveolar space that consolidates
- inflammation of alveolar septa
what 3 components make up the alveolar septa?
- alveolar epithelium
- interstitium
- capillary endothelium
outline how alveolar macrophages initiate the acute inflammatory response in Pneumonia
- infectious agent present in alveoli AND uncontrollably multiplies
- alveolar macrophages already in alveolar walls are activated by infectious agent
- alveolar macrophages engulf and digest pathogens, release cytokines and present antigens on their surface for T cells (adative immune system)
- the release of cytokines also attract neutrophils to the site of infection via chemotaxis.
why do the alveolar walls look significantly bigger than they are on staining in Pneumonia?
because the capillaries that are in the walls are so congested with blood due to the infection, causing the capillaries to bring all the components of the blood to the site of infection.
what does the term “Red Hepatisation” mean?
conversion into a substance that resembles the liver
what is grey hepatisation?
when exudates are transformed into scarring masses filled with macrophages and recruited fibroblasts that create the scar tissue.
why is there paler staining in grey hepatisation compared to red hepatisation?
because in grey hepatisation there is progressive red blood cell disintegration
when does red hepatisation occur?
occurs 2-3 days after consolidation of exudate
when does grey hepatisation usually occur
2-3 days after red hepatisation
