- The stomach has a strong muscular walls. The muscles contract and relax to churn the food an mix it with the enzymes and mucus. The mixture is called CHYME.
- The presence of food in the stomach, triggers the gastric glands (in the wall of the stomach) to secrete GASTRIC JUICE.
- The gastric juice contains PEPSINOGEN (inactive form of pepsin), HYDROCHLORIC ACID and MUCUS.
- The function of the hydrochloric acid is to provide acidic medium for the pepsin to function well (Pepsin works well at pH 2). Apart from this, it also kills any bacteria coming along with the food and activates the inactive pepsinogen into PEPSIN (REMEMBER these three functions of the hydrochloric acid). (Note: The salivary amylase from the mouth is denatured in the stomach? WONDER WHY?)
- The mucus protects the stomach wall from being attacked by the acid (REMEMBER the nature of an acid? CORROSIVE!!!)
- Any proteins present in the chyme is digested by the pepsin into POLYPEPTIDES.
NOTE: IN THE STOMACH, ONLY PROTEINS ARE DIGESTED CHEMICALLY (ALSO PHYSICALLY DUE TO THE STOMACH MUSCLE CONTRACTION). STARCH AND FATS ARE NOT DIGESTED CHEMICALLY IN THE STOMACH AS THE STOMACH DO NOT PRODUCE ENZYMES THAT CAN WORK ON STARCH AND FATS!!!
