Physiology and General Pathology
What this domain tests
This domain links normal body function with disease mechanisms: homeostasis, cell injury, inflammation, fluid balance, thrombosis, healing and neoplasia. Expect definitions plus applied interpretation.
Core rules
- Homeostasis keeps temperature, pH, glucose, electrolytes and fluid volume within narrow limits through negative feedback.
- Reversible cell injury causes swelling and fatty change; irreversible injury causes necrosis. Necrosis triggers inflammation; apoptosis is programmed, clean cell death.
- Acute inflammation has redness, heat, swelling, pain and loss of function, driven by vasodilatation and increased permeability with neutrophil exudate. Chronic inflammation shows lymphocytes, plasma cells and fibrosis.
- Transudate is low-protein fluid from hydrostatic pressure; exudate is high-protein fluid from inflammation.
- Thrombosis is clot formation in a vessel; embolism is a detached mass travelling in the bloodstream; infarction is ischemic necrosis.
- Benign tumours are well differentiated, slow-growing and non-invasive; malignant tumours invade and metastasize.
Worked example
A swollen, hot, painful appendix shows neutrophils and fibrin-rich fluid. Reasoning: the findings fit acute inflammation with an exudate. The high protein and cells distinguish it from a transudate, which would be pale and low in protein.
Traps
- Calling apoptosis a form of necrosis.
- Mixing thrombosis with embolism.
- Describing all swelling as edema without checking protein content.
- Using metaplasia and dysplasia as synonyms; metaplasia is a change of cell type, dysplasia is disordered growth.