Pathology and Pathophysiology
Pathology and Pathophysiology tests mechanisms of disease, morphological change, and laboratory interpretation. It links basic science to clinical signs.
Core rules
- Cell injury is reversible until membrane integrity and ATP production fail; necrosis is pathological, apoptosis is programmed.
- Acute inflammation has vasodilatation, permeability, and neutrophils; chronic inflammation has lymphocytes, macrophages, and fibrosis.
- Metaplasia is reversible replacement; dysplasia is disordered growth and carries cancer risk.
- Oedema follows Starling forces: hydrostatic pressure, oncotic pressure, permeability, and lymphatic obstruction.
- Acid-base: calculate compensation; anion gap acidosis suggests ketoacidosis, lactate, renal failure, or toxins.
Worked example
A 22-year-old with type 1 diabetes has glucose 28 mmol/L, pH 7.10, bicarbonate 10 mmol/L, and ketonuria. The reasoning: high anion gap metabolic acidosis with ketones is diabetic ketoacidosis. Treatment is isotonic saline, insulin after potassium is checked, and potassium replacement. Bicarbonate is not routine unless severe acidosis.
Traps
Do not confuse respiratory compensation with correction; do not call all hyperplastic growth malignant; do not miss mixed acid-base disorders; do not ignore the anion gap.