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Digestive System. Role of Digestive System A. Prepare food for absorption and utilization by all the body cells B. Excess food material (not absorbed)

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Presentation on theme: "Digestive System. Role of Digestive System A. Prepare food for absorption and utilization by all the body cells B. Excess food material (not absorbed)"— Presentation transcript:

1 Digestive System

2 Role of Digestive System A. Prepare food for absorption and utilization by all the body cells B. Excess food material (not absorbed) becomes feces to be eliminated C. Ingestion vs. Digestion 1. Ingestion – process of taking food into the GI tract 2. Digestion – a. food and fluid is broken down so the body can use them to build and nourish cells, along with providing energy b. absorption – movement of nutrients into internal environment

3 A. Gastrointestinal (GI) Tract [aka alimentary canal] (listed in order of food pathway) 1. mouth 2. oropharynx 3. pharynx 4. esophagus 5. stomach 6. small intestine a. duodenum b. jejunum c. ileum 7. large intestine a. cecum b. colon 1. ascending colon 2. transverse colon 3. descending colon 4. sigmoid colon 8. rectum 9. anus B. Accessory Organs 1. salivary glands 2. tongue 3. teeth 4. liver 5. gallbladder 6. pancreas 7. vermiform appendix

4 Layers of the walls of the gastrointestinal (GI) tract 1. (deepest) mucosa submucosa muscularis serosa (most superficial) 2. Tissue layers have variation in different organs

5 Mouth and Pharynx Buccal Cavity –Lips – external is skin; internal is mucous membranes –Cheeks – lined by mucous membranes; contain mucous secreting glands –Hard and Soft Palates Hard palate – four bones Soft palate – muscle; forms partition between mouth and nasopharynx; uvula extend from soft palate –Tongue – muscle covered by mucous membrane mastication (chewing) and deglutition (swallowing) papillae – surface of tongue; some contain taste buds lingual frenulum – mucous membrane fold that anchors tong to bottom of mouth

6 Mouth and Pharynx Salivary Glands –Secrete about 1L of saliva/day Salivary amylase – enzyme in saliva that converts starch to sugar –Three pairs of glands (parotid, submandibular, sublingual)

7 Mouth and Pharynx Teeth –Anatomy crown - covered in enamel neck – connects crown to root root – fits into socket in the gum –Types Deciduous teeth (20 baby teeth) –Incisors –Canines –first molars –second molars –third molars – wisdom teeth Permanent Teeth (32 adult teeth) –incisors –canine –premolars –Molars Pharynx – tube through which bolus (chewed ball of food) passes when moved from mouth to esophagus (deglutition)


9 Esophagus and Stomach Esophagus –Extends from pharynx to stomach –Resides in both abdominal and thoracic cavities –Peristalsis begins

10 Esophagus and Stomach Stomach –Functions reservoir for food secretes gastric juice breaks food into small particles and mixes them with gastric juice limited absorption helps protect body from bacteria swallowed with food produces gastrin – (hormone that causes the stomach to produce acid)

11 Esophagus and Stomach Stomach –Sphincter Muscles lower esophageal sphinter (LES)/cardiac sphincter - controls opening of esophagus into stomach pyloric sphincter - controls opening of stomach into small intestine (duodenum) –gastric reflux – sphincter working improperly causing heartburn –Stomach wall Gastric mucosa –Rugae – folds in lining of the stomach gastric glands – below rugae; secrete most of gastric juice –chief cells – secrete the enzymes of gastric juice –parietal cells - secrete HCl »Zantac – reduces HCl formation in stomach –endocrine cells – secrete gastrin Gastric muscularis – thick layer of muscle that allows stomach to contract

12 Helicobacter pylori – bacteria that causes peptic ulcers Stomach lining replaces itself every 3 days Chyme – liquefied food; form that food leaves the stomach Gastroenteritis – stomach inflammation Emesis – vomiting 35 million digestive glands in the stomach

13 Gastroesophageal Reflux

14 Gastric Ulcer

15 Small Intestine Proximal to stomach duodenum jejunum ileum Microvilli (villus) allow for absorption (increase surface area by hundreds) Where majority of substances are absorbed 22 feet long Food can stay here for up to 4 hours

16 Large Intestine

17 Proximal to small intestine cecum ascending colon traverse colon descending colon sigmoid colon rectum Haustra – pouchlike structures Constipation – movement of lower colon and rectum contents at a rate slower than normal Diverticulosis – outpouchings of intestinal wall Colitis – inflammation of large intestine 5 feet long Waste stays 10-12 hours Main function is water absorption in order to eliminate feces

18 Appendix and Peritoneum Vermiform Appendix –function not fully known; but thought to provide safe place for good bacteria –appendicitis inflammation of appendix not common in elderly appendectomy – surgical removal of appendix Peritoneum –large, continuous sheet of serous membrane –parietal and visceral portions –mesentery – extension of parietal peritoneum that anchors GI tract to abdominal wall.


20 Liver Anatomical units – lobes and lobules –left lobe –right lobe – biggest section of liver –hepatic lobules – branch of hepatic vein extends through each lobule (main anat unit) Blood flows to hepatic lobules via branches of the hepatic artery and hepatic portal vein Common bile duct – merger of the hepatic duct and cystic duct Produces bile –Bile salts – aid in the absorption of fats; most essential part of bile –No enzymes Functions of liver –Detox –Bile secretion – secrete 1 pint/day –Metabolizes proteins, fats, and carbohydrates Misc. Info –Hepatic refers to liver –Largest gland in the body –Hepatitis – inflammation of the liver –Cirrhosis – degenerative liver condition –Removes harmful substances from the blood –Stores vitamins and sugars until your body needs them


22 Gallbladder –Stores bile (holds 30-50 ml bile) –Cholecystokinin (CCK) – hormone that stimulates gallbladder to release bile into duodenum (small intestine) –Secretin – stimulates release of bile –Cholelithiasis - gallstones –Cholecystectomy – surgical removal of gallbladder –Below liver –Pear shaped

23 Cholelithiasis - Gallbladder with yellow cholesterol gallstones Cholecystectomy Gallbladder before removal

24 Pancreas –Both endocrine and exocrine gland –Pancreatic juice secreted by exocrine acinar cells –Pancreatic cancer – form of adenocarcinoma –Breaks down sugar –Beta cells secrete insulin

25 Digestive Physiology Mechanical Digestion Mastication Deglutition Oral stage – mouth to oropharynx - voluntary control - bolus formed - soft palate acts as valve to prevent food from enetering nasopharynx Pharyngeal stage – oropharynx to esophagus - involuntary control - epiglottis prevents bolus from entering larynx to trachea Esophageal stage – esophagus to stomach - involuntary control

26 Peristalsis wavelike ripple of smooth muscle ring of contraction occurs where GI wall is stretched, pushing bolus forward stimulated by CCK – secreted by endocrine cells in presence of chyme Segmentation mixing movement forward and backward movement that mechanically breaks down food and mixes it with digestive juices

27 OrganMechanical Process Mouth (teeth and tongue)Mastication Deglutition PharynxDeglutition EsophagusDeglutition Peristalsis StomachChurning Peristalsis Small IntestineSegmentation Peristalsis Ascending and Transverse Colon Segmentation Peristalsis Descending ColonMass peristalsis RectumDefecation

28 Chemical Digestion Digestive enzymes a. extracellular, organic (protein) catalysts b. enzyme action 1. specificity 2. optimal pH StomachJejunumIleumColon pH3.06.0- 3. catalyst 4. continually destroyed or eliminated, so constantly being made

29 Digestive Enzyme Action proenzyme altered by kinase to form active enzyme 1. kinase removes prosthetic group to expose active site 2. substrate (food) binds to active site of active enzyme 3. enzyme splits substrate into components and releases them 4. enzyme can now digest new substance

30 Carbohydrate digestion (bread, potato, rice, pasta, fruit, vegetables) Starch and sugar are broken down by saliva, pancreatic and small intestinal juices salivary amylase, small intestine pancreatic juices enzymes * starch maltose glucose (monosac) absorbed into blood liver (stored or used) small intestine enzymes * sugar (sucrose) glucose + fructose absorbed into blood * fiber – undigestible Cellulose cannot be broken down; eliminated in feces

31 Pepsin Trypsin

32 Lipid Digestion emulsification – bile breaks down fat into small droplets within the small intestine Steatorrhea - impaired fat absorption producing large, greasy, foul-smelling stool Fat-soluble vitamins – A, D, E, K (stored in liver and fatty tissue) Pancreatic lipase – main fat- digesting enzyme

33 Digestive JuiceEnzymeSubstance Digested End Product SalivaSalivary amylase Starch (polysacc) Maltose (monosacc) Gastric JuiceProtease (pepsin) ProteinPartially digested protein Pancreatic JuiceProtease (trypsin) ProteinsPeptides and a.a. LipaseFatsFatty acids, glycerol Pancreatic Amylase Starch (polysacc) Maltose (monosacc) IntestinalPeptidasesPeptidesa.a. SucraseSucroseGlucose, fructose LactaseLactoseGlucose, galactose MaltaseMaltoseGlucose

34 Disorders Mumps Tooth Decay Malocclusion GERD (gastroesophageal reflux disease) Ulcers Pyloric stenosis Appendicitis Hemorrhoids Proctitis Diabetes Gastroenteritis Anorexia Nausea Emesis Diarrhea Constipation Malabsorption Diverticulitis Colitis Irritable Bowl Syndrome Colorectal Cancer Hepatitis Cirrohsis Pancreatitis Pancreatic cancer

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