The inner layer of the human stomach produces hydrochloric acid with a pH of about 2.0—in other words, the acid is so strong, if a piece of wood were to drop into your stomach, it would break down very rapidly. Thus, special epithelial cells that line your stomach produce a bicarbonate-rich solution that is alkaline (basic), with a higher pH that counteracts the acid produced by the stomach. Because of this, cells are protected from the digestive enzymes at work in the stomach, but if stomach acid manages to reach the tissue below the protective mucus layer, gastric ulcers can result. (Another type of stomach ulcer, caused by the bacteria Helicobacter pylori, can impair the stomach’s defenses.)