Serial analysis of vitreous humour at increasing postmortem intervals shows predictable directional changes in its major electrolytes. Which pair of vitreous electrolytes shows a gradual DECLINE after death?

• A Potassium and phosphate
• B Bicarbonate and urea
• C Calcium and magnesium
• D Sodium and chloride ✓

Explanation

With increasing postmortem interval, vitreous potassium, phosphate and hypoxanthine all rise, while sodium and chloride fall gradually. The decline of sodium and chloride reflects passive equilibration and dilution across membranes losing their gradients as autolysis proceeds. This reciprocal pattern, rising potassium alongside falling sodium and chloride, is why ratios such as sodium to potassium have been proposed for decomposed bodies. Urea does not decline because it diffuses poorly out of the vitreous chamber.

Reference: Knight's Forensic Pathology, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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