Digestive System
Parts of the digestive system. Salivary glands
Pharynx mouth and teeth Esophagus
Salivary glands
Stomach
Liver Gall bladder
Bile duct
Pancreas
Large intestine Small intestine Rectum
Stomach and Intestines
protein complex molecule made from amino acids; used in cells for structure, signaling, and controlling reactions
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The stomach is a muscular sac that is located in the upper left portion of the abdominal cavity. The inner lining of the stomach wall contains millions of tiny gastric glands that secrete gastric juice, which dissolves the food to form a thick liquid called chyme. Gastric juice contains several substances including hydrochloric acid, intrinsic factor (which is essential for the intestinal absorption of vitamin B12) and pepsinogen (an inactive proteindigesting enzyme). The hydrochloric acid has several functions including destroying ingested bacteria, and converting pepsinogen into its active form, pepsin, in order to initiate the digestion of protein. At the lower end of the stomach is the pyloric sphincter, a valve through which chyme must flow to enter the small intestine. Most meals are gradually emptied into the small intestine after two to six hours due to peristaltic contractions that travel toward the lower end of the stomach. Most digestion and absorption occur within the small intestine. The small intestine consists of three segments named the duodenum, jejunum and ileum. The duodenum receives chyme from the stomach as well as pancreatic juice from the pancreas and bile from the liver (and stored in the gallbladder).