The path of digestion begins in the mouth when food is broken down mechanically, into smaller pieces, by the teeth and tongue. The complex carbohydrates found in the food are also broken down chemically with the help of the enzyme (ptyalin), found in saliva. The food is then mixed and turned into a swallow ready material known as bolus. When the bolus is swallowed, it travels through a muscular tube known as the esophagus. It is then allowed into the stomach by passing through the cardiac sphincter. Once in the stomach, the bolus moves from the upper portion of the stomach (fundus) to the middle section (the body). In the stomach body, food is broken down further by the stomach wall and gastric juices which initiates the absorption of vitamin B12. The food is then slowly moved into the last part of the stomach (pylorus) in the form of a semi liquid mass called chyme. When chyme enters the pylorus it triggers an increase in the release of gastric juices. The gastric juices contain hydrochloric acid which destroys bacteria and makes calcium and iron more absorbable. While in the pylorus proteins are broken down by the enzyme pepsin. Two other enzymes, rennin and casein, are found in children. These two enzymes aid in the digestion of milk proteins. The chyme then exits the stomach, through the pyloric sphincter, and into the small intestine. Food continues its digestive path in the small intestine. Enzymes from the pancreas are released into the small intestine to help digestion. As their names imply; pancreatic proteases break down proteins; pancreatic lipase break down fat; and pancreatic amylase break down carbohydrates. The small intestine enzymes (lactase, maltase and sucrase) break down their respective enzymes into simple sugars and the enzyme peptidases break down proteins into amino acids. Bile, produced by the liver and stored in the gallbladder, is released into the small intestine. The bile is triggered by the hormone (CCK) in order...
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