The inner mucous membrane (lining) has large folds that are visible to the naked eye. These folds run toward the exit of the stomach, providing “pathways” along which liquids can quickly flow through the stomach. If you look at the mucous membrane under a microscope, you can see lots of tiny glands. There are three different types of glands. These glands make digestive enzymes, hydrochloric acid, mucus and bicarbonate.
Gastric juice is made up of digestive enzymes, hydrochloric acid and other substances that are important for absorbing nutrients – about 3 to 4 liters of gastric juice are produced per day. The hydrochloric acid in the gastric juice breaks down the food and the digestive enzymes split up the proteins. The acidic gastric juice also kills bacteria. The mucus covers the stomach wall with a protective coating. Together with the bicarbonate, this ensures that the stomach wall itself is not damaged by the hydrochloric acid.