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THE FUNCTION OF THE GASTROINTESTINAL SYSTEM,
MOUTH, TEETH, SALIVARY GLANDS The function of the teeth is to break the food into smaller pieces to enable swallowing and quicker digestion. The salivary glands secrete mucous to aid in swallowing and an enzyme, amylase, which breaks down starches into simpler carbohydrates and are easier to digest. ESOPHAGUS The esophagus is a muscular tube which passes the food from the mouth into the stomach. Regular contractions propel the food. STOMACH The stomach is a storage and mixing organ. It has great distendibility and is able to receive and hold relatively large amounts of food. There is a muscle at the lower end of the esophagus which prevents food from backing up and a sphincter at the lower end of the stomach which regulates the passage of food out of the stomach. The stomach contracts rhythmically and churns the food. Acid is mixed with the food to aid in digestion. Enzymes are secreted by the stomach to assist in the digestion of proteins. Small amounts of food are expelled from the stomach into the duodenum on a regular basis until the stomach is empty. DUODENUM The duodenum is the first part of the small bowel. The major part of the digestion begins to take place in the duodenum. Iron is predominantly absorbed in the duodenum. PANCREAS The pancreas is important in that it secretes most of the major enzymes necessary for the digestion of food. It secretes tryspsin which breaks down protein into amino acids. It secretes lapase which breaks down fat into free fatty acids. Amylase which breaks down carbohydrates into simpler sugars is also secreted by the pancreas. The Pancreas produces insulin which regulates the body’s metabolism of glucose. LIVER The liver is the largest organ in the body. The liver manufactures all the major body proteins. It regulates the body cholesterol, secretes waste products from the blood and metabolizes and excretes many drugs. The major function of the liver in digestion is the production and excretion of bile salts. Bile salts are detergents which keep the fat in the intestine in solution so it can be digested and absorbed. Bile secreted from the liver passes down the bile duct to the gallbladder where it is stored and concentrated. SMALL BOWEL The small bowel is a muscular tube 15 feet long and is the major site for ingestion and absorption. The upper half is the jejunum and the lower half is the ileum. The amino acids and the free fatty acids are absorbed into the cells lining the small bowel and enter the blood. The lining cells contain enzymes which break down complex sugars into very simple sugars which are then absorbed and enter the blood. Water, electrolytes, vitamins and minerals are also absorbed in the small bowel. The small bowel contracts regularly from above downward passing the food down over a period of three to four hours. LARGE BOWEL The large bowel is the colon and is approximately 5 feet long. The parts are the ascending colon, transverse colon, descending colon, sigmoid colon and rectum. The main function of the colon is the absorption of water and storage of the stool. The colon contracts toward the rectum when the feces enter the rectum and distend it, there is the urge to defecate. More intense contractions occur. The anus is the muscle which regulates the passage of stool out of the body. via The 44 |