Salivary Buffers — MFDS Part 1 MCQ

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HardPhysiologySalivary BuffersMFDS Part 1

Paraffin stimulation increases whole-saliva flow and raises its pH. Over the physiologically relevant pH range from 7.0 to 5.0, which salivary buffer system makes the principal flow-dependent contribution to the increased buffering capacity of stimulated saliva?

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Correct answer: C — Bicarbonate buffer system

The correct answer is C, the bicarbonate buffer system. Salivary stimulation markedly increases bicarbonate concentration and raises salivary pH, making bicarbonate the principal flow-dependent buffer over approximately pH 7–5. Phosphate makes a relatively greater contribution at low, unstimulated flow but does not show the same increase with stimulation. Ionisable groups on salivary proteins contribute to buffering and become particularly important at more acidic pH, around pH 5–4, which is outside the range specified. Urea can indirectly generate alkali through bacterial urease activity, and ammonia can accept hydrogen ions, but neither is the predominant physiological buffer system responsible for the increased buffering capacity of stimulated whole saliva.

Reference: Bardow A, Moe D, Nyvad B, Nauntofte B. The buffer capacity and buffer systems of human whole saliva measured without loss of CO2. Archives of Oral Biology. 2000;45(1):1–12. https://pubmed.ncbi.nlm.nih.gov/10669087/