Well the answer of this question is very long. But now I am going to give you a brief answer.The lean meat is subjected to both muscular movements and chemical reactions in the stomach. The gastric glands in the wall of stomach secrete gastric juice. The gastric glands consist of 3 kinds of cells: chief cells filled with secretory granules containing pepsinogen, Oxyntic cells which secretory hydrochloric acid, and mucous cells which secrete mucus. The HCL kills several bacteria that are swolled with the food. It converts pepsinogen into active pepsin and provides an acetic medium for the action of pepsin. From the stomach, the semi digested food passes into the small intestine, where it is fully digested. Into this region of the digestive tract three secretions are poured. These are pancreatic juice, intestinal juice and bile.