Bicarbonate diffusion through mucus

A mathematical method to study the movement of bicarbonate through the duodenal mucus indicates that the convection of fluids plays an important role in maintaining the pH of the intestine. The pH of the epithelial surface is almost neutral although a large amount of acid is secreted into it and the low levels of bicarbonate are inadequate to maintain the pH. A mucus barrier is formed into which the bicarbonate is secreted to neutralize the pH.