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Digestive System Yixuan He Function • • • • • Break up food into smaller pieces. Transporting food to the GI tract (gastrointestinal) Secreting digestive enzymes Absorbing nutrients into the blood Excreting solid waste products (waste) Mouth • The mouth is the beginning of the digestive tract • Chewing breaks the food into small pieces • Easily digested Pharynx and Esophagus • Pharynx • The throat • Receives the food from your mouth. • Swallowing • A voluntary reflex • Esophagus • Connects mouth to stomach • A muscular tube extending from the pharynx and behind the trachea to the stomach • Food is pushed through the esophagus and into the stomach by means of a series of contractions called peristalsis. Stomach • Storage bag for food • Secretes acid and powerful enzymes that bread down the food and change it to a consistency of liquid or paste. • Flexible • Expands when you eat • Can hold up to 3 L of food • If the stomach could not store food, you would have to eat every twenty minutes or so instead of just three times a day. Small Intestine • folded into tiny fingerlike projections called villi • Each villus contains blood vessels. • surface area through which nutrients pass to the bloodstream is greatly increased • If the villi on the inner lining of the small intestine are flattened out, they would cover about 4500 square meters. • Where most of the nutrient is absorbed through the walls and into the bloodstream • Breaks down food • Duodenum, Jejunum, and Ileum • Duodenum is largely responsible for the continuing breakdown process • Jejunum and ileum being mainly responsible for absorption of nutrients into the bloodstream. Large Intestine (colon) • five- to seven -foot -long muscular tube that connects the small intestine to the rectum • absorb water from the undigested food, hold the undigested food for a while and then excrete it as feces. • Consists of: • • • • • cecum ascending colon transverse colon descending colon sigmoid colon Rectum and Anus • Rectum • receives stool from the colon • stores some feces and help with defecation • Anus • dispose of waste products out of the body Accessory organs • • • • • Salivary Glands Liver Pancreas Gallbladder Sphincters Salivary Glands • Saliva mixes with food to begin the process of breaking it down. • Fun fact: The smell of food triggers the salivary glands in your mouth to secrete saliva, causing your mouth to water. When you actually taste the food, saliva increases. Liver and Pancreas • Liver • The largest organ inside the body • It produces bile, a substance that helps in the digestion of fats. • Process the blood coming from the small intestine. • Purifies this blood of many impurities before traveling to the rest of the body. • Pancreas • Produce pancreatic juice • Pancreatic juice helps in neutralizing or weakening the acid in food inside the stomach. • Also contains different enzymes that are needed to further break down starch, proteins and fats in the small intestine. Gallbladder and Sphincters • Gallbladder • Small muscular sac • Storage sac for excess bile. • Sphincters • Lower Esophagus Sphincter • Located Just before the opening to the stomach • Ring-shaped muscle • This sphincter opens to let food pass into the stomach and closes to keep it there. • If your LES doesn't work properly, you may suffer from a condition called GERD which causes heartburn and regurgitation • anal sphincters (inner and exterior) • control the exit of feces from the body Physical digestion vs. Chemical digestion • Physical • is the breakdown of food by physical means. • Chemical • molecules of water, vitamins, and minerals are small enough to be absorbed through the intestinal wall and into the blood stream • proteins, carbohydrates, and fat molecules are too large and must be broken down further by chemical means. This is chemical digestion. Physical digestion vs. Chemical digestion Chemical Physical • breakdown of food by physical means • Chewing and churning • Digest food and aid in absorbing nutrients. • breakdown of food by chemical means • Acids and enzymes Nutrients • Carbohydrates: • Saliva begins carbohydrate digestion with the enzyme salivary amylase. • The release of Pancreatic Amylase in the duodenum digests the rest • Protein • Begins in the stomach with HCl and Pepsin. • Inside the small intestine, the pancreatic enzymes trypsin and chymotrypsin break down the polypeptides. • Lipid • The fat digesting enzyme lingual lipase starts breaking down fat inside your mouth as you are chewing. • Bile released from the gall bladder Crohn’s Disease • a chronic inflammatory condition of the gastrointestinal (GI) tract. • Symptoms: • • • • abdominal pain diarrhea weight loss poor appetite • Crohn’s disease may affect as many as 700,000 Americans. • Crohn's is more prevalent among adolescents and young adults between the ages of 15 and 35. • Treatment: • Medication • Surgery Irritable Bowel Syndrome (IBS) • Irritable bowel syndrome is a functional gastrointestinal (GI) disorder, meaning it is a problem caused by changes in how the GI tract works. • Symptoms • • • • Diarrhea Constipation Passing mucus Abdominal bloating • Affects 3 to 20 percent of the population • Treatment: • Changes in eating, diet, and nutrition • Medication • Probiotics Bibliography • National Digestive Diseases Information Clearinghouse (Division of NIDDK/NIH). American Medical Association. • The Cleveland Clinic Foundation • http://my.clevelandclinic.org/anatomy/digestive_system/hic_the _structure_and_function_of_the_digestive_system.aspx • Crohn's and Colitis Foundation of America • National Digestive Diseases Information Clearinghouse • http://digestive.niddk.nih.gov/ddiseases/pubs/ibs/ Bibliography (Cont.) • Pictures: • • • • • • http://www.google.com/imgres?hl=en&sa=X&tbo=d&biw=1052&bih=535&tbm=isch&tbnid=R9Klud4RSyZ2XM:&imgrefurl=http://www.encognitive.com/node/1122&docid=XQFBGcRLNkvv GM&imgurl=http://www.encognitive.com/images/digestive-system2.jpg&w=422&h=561&ei=r6sAUdveDMaK2gWyj4HoDA&zoom=1&iact=hc&vpx=451&vpy=137&dur=794&hovh=259&hovw=195&tx=125&ty=138&sig=113692303009654574651&page=1&t bnh=153&tbnw=121&start=0&ndsp=14&ved=1t:429,r:3,s:0,i:160 http://www.google.com/imgres?hl=en&sa=X&tbo=d&biw=1052&bih=535&tbm=isch&tbnid=jWClj7x4y8kMM:&imgrefurl=http://en.wikipedia.org/wiki/Human_pharynx&docid=Ce2Gcs2udEo3eM&imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/Illu01_head_neck .jpg/250pxIllu01_head_neck.jpg&w=250&h=254&ei=FawAUdnWLqiG2gXFpICwDg&zoom=1&iact=hc&vpx=4&vpy=158&dur=4080&hovh=203&hovw=200&tx=76&ty=119&sig=11369230300965457465 1&page=1&tbnh=139&tbnw=146&start=0&ndsp=18&ved=1t:429,r:0,s:0,i:151 http://www.google.com/imgres?hl=en&tbo=d&biw=1052&bih=535&tbm=isch&tbnid=uRaNeVBRR10iYM:&imgrefurl=http://uogirl10-virtualfieldtrip.blogspot.com/2008/05/post8.html&docid=vOXad7FMIKH2fM&imgurl=http://2.bp.blogspot.com/_pGhDYqqlW5U/SCJvbH59zKI/AAAAAAAAACs/BVCq11bhi4U/s400/Stomach.gif&w=300&h=243&ei=TKwAUbavCjs2AXekoDwDg&zoom=1&iact=rc&dur=359&sig=113692303009654574651&page=1&tbnh=149&tbnw=187&start=0&ndsp=11&ved=1t:429,r:8,s:0,i:172&tx=120&ty=88 http://www.google.com/imgres?um=1&hl=en&sa=N&tbo=d&biw=1052&bih=535&tbm=isch&tbnid=ibjJ20Hhr_6vfM:&imgrefurl=http://students.cis.uab.edu/ashjones/index3a.html&docid =VbAAZkvKEOsP9M&imgurl=http://students.cis.uab.edu/ashjones/colon3.jpg&w=396&h=300&ei=rKwAUZSxNuX72QWi54GYAw&zoom=1&iact=rc&dur=465&sig=113692303009654574651 &page=1&tbnh=134&tbnw=177&start=0&ndsp=11&ved=1t:429,r:3,s:0,i:160&tx=127&ty=59 http://www.google.com/imgres?um=1&hl=en&sa=N&tbo=d&biw=1052&bih=535&tbm=isch&tbnid=BAURNyL0fQZLwM:&imgrefurl=http://www.alargastro.com/Patient_Education/Large_I ntestine.html&docid=v6ZGgB1mjYNowM&imgurl=http://www.alargastro.com/images/Large%252520Intestine.jpeg&w=460&h=300&ei=Ba0AUdWPC4rm2QWkl4DADg&zoom=1&iact=hc& vpx=569&vpy=217&dur=1733&hovh=181&hovw=278&tx=211&ty=116&sig=113692303009654574651&page=1&tbnh=133&tbnw=204&start=0&ndsp=16&ved=1t:429,r:8,s:0,i:175 http://www.google.com/imgres?um=1&hl=en&tbo=d&biw=1052&bih=535&tbm=isch&tbnid=cBPuui51denENM:&imgrefurl=http://www.cpmc.org/advanced/liver/patients/topics/Pancrea sCancer-profile.html&docid=lqQQGXFzlRNj3M&imgurl=http://www.cpmc.org/images/liver/topics/PancreasCancer-profile0.jpg&w=260&h=288&ei=Uq0AUYLxCorm2QWkl4DADg&zoom=1&iact=hc&vpx=803&vpy=140&dur=1788&hovh=230&hovw=208&tx=177&ty=110&sig=113692303009654574651&page=1& tbnh=144&tbnw=130&start=0&ndsp=18&ved=1t:429,r:17,s:0,i:133