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THE HUMAN DIGESTIVE SYSTEM Label the following diagrams. ____________________________________________________________________________________________________________ 493713785 Page 1 of 9 PARTS OF THE HUMAN DIGESTIVE SYSTEM STRUCTURE FUNCTION MOUTH A) teeth number of teeth arranged along the upper and lower jaws used in physical digestion B) uvula hangs from the middle of the back edge of the soft palate prevents food from entering the pharynx when swallowing C) salivary glands there are three sets of salivary glands: parotid glands (largest), the sublingual glands (smallest) and submaxillary glands these glands produce saliva that enters the mouth through a duct the saliva assist in the chemical digestion of starch and glycogen, it also helps to lubricate the food before passing into the next part of the digestive system D) tongue the upper surface of the tongue is covered with tiny pimple-like structures called papillae which contains a number of taste buds that has the ability to determine if something is sweet, sour, bitter, salty, or some combination thereof the tongue also aid in mixing the food and saliva to together to form the bolus which is pushed to the back of the pharynx EPIGLOTIS when swallowing the esophagus and trachea move up causing the trachea to come in contact with the epiglottis which prevents liquids and solids (food) from entering the trachea ESOPHAGUS a muscular structure that receives the bolus from the mouth contains a number of small tubular glands that secrete mucin which is used to lubricate the bolus as it moves from the mouth to the stomach the esophagus contains circular and longitudinal muscles which are used to move the food in a forward direction through a process called peristalsis (is a series of wave like contractions. STOMACH at the top of the stomach is a ring like structure called the cardiac sphinster which allow the bolus to pass into the stomach and prevent partially digested food from entering the esophagus stomach is a muscular, J-shaped, sac-like organ the stomach lining is packed with millions of gastric glands which secrete gastric juice which start to digestion of proteins the stomach contain three muscular layers; circular, longitudinal and oblique layer which work together to break food physically into smaller pieces and mix it with the gastric juices, rendering it into a thick liquid called chyme gastric juice cause the chyme to become acidic at the end of the stomach is a muscular valve called the pyloric sphincter which controls the movement of chyme into the small intestine ____________________________________________________________________________________________________________ 493713785 Page 2 of 9 ____________________________________________________________________________________________________________ 493713785 Page 3 of 9 SMALL INTESTINE A) duodenum subdivided into three regions contains only circular and longitudinal muscles is generally U-shaped, and is the shortest and widest of these regions. the pancreatic and bile ducts open into the duodenum, to further aid in the digestion of carbohydrates, proteins and fats carbohydrates are broken down into monosaccharides (glucose, fructose and galactose proteins are broken down into amino acids fats are broken down into glycerol and three fatty acids the neutralization of the acidic chyme the absorbing surface area of the duodenum is increased by i) a number of folds in the mucous membrane ( SA 3X) ii) a number of tiny projections called villi (sing. villus) ( SA 30X) iii) each villi contains a fine brush like boarder called microvilli ( SA 600X) between the villi are intestinal glands that secrete intestinal juices the villi will absorbs the nutrients produced by chemical digestion and passes them into the circulatory system inside the villi is a lacteal that absorbs large fat molecules from the intestine the lacteal is connected to the lymphatic system which will connect to the circulatory system B) jejunum is about 2.5 m long contains more folds and intestinal glands than the duodenum its function is to break down remaining proteins and carbohydrates so the end products can be absorbed C) ileum is about 3 m long contains fewer and smaller villi its function is also to absorb nutrients, to push remaining undigested material into the large intestine. ____________________________________________________________________________________________________________ 493713785 Page 4 of 9 ____________________________________________________________________________________________________________ 493713785 Page 5 of 9 LARGE INTESTINE At about 1.5 m long The large intestine consists of the caecum, colon, rectum, and anal canal A) caecum The sac-like caecum is the blind end of the large intestine. B) appendix hangs suspended from the caecum an organ that plays no role in digestion but which may play some role in fighting infection C) colon the main portion of the large intestine undigested food moving up, along, and down the colon water and dissolved minerals are absorbed from the undigested food, intestinal bacteria help to i) break the undigested food down further to provide more nutrients ii) produce vitamins B-12 and K and some amino acids the damp mass of indigestible material that remains at the end of this process is called feces D) rectum is the last 20 cm of the large intestine feces is passed into the rectum and anal canal E) anus the feces passes out of the body through the anus, which has rings of circular muscle called the anal sphincters. these sphincters allow the body to control the timing of elimination of waste to some extent. ____________________________________________________________________________________________________________ 493713785 Page 6 of 9 The Roles of Related Organs Three other organs associated with the digestive tract are the liver, pancreas, and gall bladder. These organs play vital roles in the digestive process. The liver also carries out many other functions essential to the body's general good health, some of which have an impact on the digestive process. LIVER largest organ in the body and has been identified as having over 500 different functions. In digestion: produces bile salts from cholesterol. bile salts are released into the small intestine as needed bile is used to break up fat globules into tiny fat droplets (emulsifies the fat) the emulsified fat is broken down by an enzyme called lipase which is activated by bile the resulting fatty acid and glycerin molecules are engulfed through pinocytosis by the epithelial cells of the villi. once inside the villi, the fatty acid and glycerin molecules enter the lacteal vessels, where they frequently reunite to make fat molecules. these molecules are then transported by the lacteal vessels through the lymphatic circulatory system and into the main bloodstream near the left shoulder. GALL BLADDER PANCREAS serves as the storage warehouse for bile produced in the liver. bile contains a number of chemicals that include cholesterol and the bile salts so important to the digestion of fats. the bile to enter the duodenum via the bile duct. as lipids are absorbed by the intestine, so are the components of bile which are carried back to the liver to be recycled back into bile the pancreas is the source of several enzymes that act on carbohydrates, fats, and peptides (smaller units of proteins) produces and releases a basic solution that changes the pH of chyme (from a strongly acid mixture to a weakly basic one) after it enters the duodenum. ____________________________________________________________________________________________________________ 493713785 Page 7 of 9 ____________________________________________________________________________________________________________ 493713785 Page 8 of 9 The Movement of Food The movement of food is accomplished by a series of wavelike muscular contractions and relaxations known as peristalsis. Peristalsis involves the circular and longitudinal muscles that surround the various parts of the digestive tract. To move food, the circular muscles over a food mass relax while the longitudinal muscles immediately in front of it contract. the circular muscles immediately behind the food mass then contract while the longitudinal muscles over the food mass relax. As succeeding muscular regions relax and contract, the food is pushed along ____________________________________________________________________________________________________________ 493713785 Page 9 of 9