ABSTRACT
The pH of GI secretions varies widely (Table 27.1). Of particular note is the acidity of gastric secretions, which results from hydrochloric acid secretion. The resting secretion of hydrogen (H+) ions of 2mmol/h can increase to up to 20 mmol/h on ingestion of food. The mucosa of the stomach is protected from the H+ ions in the gastric juice by the active secretion of bicarbonate ions which, without noticeably altering the pH of gastric contents, adequately buffer any acid that may succeed in penetrating the mucus covering the epithelium.
