Digestion in the Stomach
• Food, once it is swallowed, may remain in
the stomach for up to 4 hours.
• Embedded in the folds of the stomach wall
are glands that secrete HCl, pepsin, and
• HCl activates pepsin (enzyme), which
breaks down proteins.
• Carbohydrates and fats continue to be
mechanically broken down by muscular
contractions in the stomach, but are not
acted upon chemically.
• Mucus, secreted by special cells in the
stomach, help protect it from gastric
juices (combination of HCl and pepsin).
• If the mucus levels become low, the
gastric juices begin to digest the stomach
wall, which leads to an ulcer.
• Eventually, the stomach contents turn into
a thick, uniform liquid called chyme.