Caseating (necrosis) and non-caseating granulomas

Granulomas
- nodular inflammatory lesions
- ball-like collection of immune cells trying to destroy a foreign substance
- containing compactly grouped modified phagocytes
- such as epithelioid cells, giant cells, and other macrophages


Caseating granulomas
- necrosis present
- appears cheese-like to unaided eye (don't expect to see this on microscope)
- typically a feature of the granulomas of tuberculosis
- tend to have infectious causes

Caseating lung due to TB

Caseating granulomas microscopic

Non-caseating granulomas
- necrosis not present
- does not appear cheese-like to unaided eye

Non-caseating granulomas microscopic

Difference between pneumocyte type I and type II

Pneumocyte Type I
- responsible for gas exchange in the alveoli and cover a majority of the alveolar surface area
- large, thin and stretched

Pneumocyte Type II
- responsible for the production and secretion of surfactant (dipalmitoylphosphatidylcholine) which reduce surface tension
- granular and roughly cuboidal in shape
- can differentiate into type I