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Digestive System Unit 11 Role of Digestive System A. Prepare food for ______________ and utilization by all the body cells B. Excess food material (not absorbed) becomes _______to be eliminated C. Ingestion vs. Digestion 1. Ingestion – process of taking food ______ the GI tract 2. Digestion - food undergoes a chemical process called __________________________ a. food and fluid is broken down into their smallest parts so the body can use them to build and nourish cells, along with providing energy b. absorption – movement of nutrients into internal environment A. Gastrointestinal (GI) Tract [aka alimentary canal] (listed in order of food pathway) 1. 2. 3. 4. 5. 6. mouth oropharynx pharynx esophagus stomach small intestine a. duodenum b. jejunum c. ileum 7. large intestine a. cecum b. colon 1. 2. 3. 4. 8. rectum 9. anus B. Accessory Organs 1. 2. 3. 4. 5. 6. 7. salivary glands tongue teeth liver gallbladder pancreas vermiform appendix ascending colon transverse colon descending colon sigmoid colon Layers of the walls of the gastrointestinal (GI) tract 1. (deepest) mucosasubmucosamuscularisserosa (most superficial) 2. Tissue layers have variation in different organs Mouth and Pharynx • __________________ Cavity – Lips – external is skin; internal is mucous membranes – Cheeks – lined by mucous membranes; contain mucous secreting glands – Hard and Soft Palates • Hard palate – _______ bones • Soft palate – _______________; forms partition between mouth and nasopharynx; uvula extend from soft palate – Tongue – muscle covered by mucous membrane • mastication (_____________) and deglutition (____________________) • papillae – surface of tongue; some contain taste buds • lingual frenulum – mucous membrane fold that anchors tong to bottom of mouth Mouth and Pharynx • Salivary Glands – Secrete about __L of saliva/day • Salivary amylase – ________ in saliva that converts starch to sugar – ___ pairs of glands (parotid, submandibular, sublingual) Mouth and Pharynx • Teeth – Anatomy • crown - covered in enamel • neck – connects crown to root • root – fits into socket in the gum – Types • ________________ teeth (20 baby teeth) – – – – Incisors Canines first molars second molars • Permanent Teeth (32 adult teeth) – – – – – • incisors canine premolars 1st & 2nd Molars third molars – wisdom teeth Pharynx – tube through which bolus (chewed ball of food) passes when moved from mouth to esophagus (deglutition) Esophagus and Stomach • Esophagus – Extends from ________ to stomach – Resides in both abdominal and thoracic cavities – Peristalsis __________ Esophagus and Stomach • Stomach – Functions • reservoir for food until it is partially digested and moved along GI tract • secretes ________ juice • breaks food into small particles and mixes them with gastric juice • limited absorption • helps protect body from bacteria swallowed with food • produces ____________ – hormone that causes the stomach to produce acid Esophagus and Stomach • Stomach – Sphincter Muscles • lower esophageal sphinter (LES)/cardiac sphincter controls opening of esophagus into ____________ • pyloric sphincter - controls opening of stomach into ___________ intestine (duodenum) – gastric reflux – sphincter working improperly causing heartburn – Stomach wall • Gastric mucosa – ____________ – 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___________l » Zantac – reduces HCl formation in stomach – endocrine cells – secrete ____________ • Gastric muscularis – thick layer of muscle that allows stomach to contract Gastroesophageal Reflux Gastric Ulcer • • • • • • Helicobacter pylori – bacteria that causes ____________ ulcers Stomach lining replaces itself every _____ days _____________ – liquefied food; form that food leaves the stomach Gastroenteritis – stomach inflammation ____________ – vomiting _____ million digestive glands in the stomach Small Intestine • Proximal to stomach duodenumjejunumileum • Microvilli (villus) allow for _________________ (increase surface area by hundreds) • Where majority of substances are absorbed • ______ feet long • Food can stay here for up to ____ hours Large Intestine Large Intestine • Proximal to small intestine cecum ascending colontraverse colondescending colonsigmoid colon rectum • _____________ – pouchlike structures • Constipation – movement of lower colon and rectum contents at a rate slower than normal • __________________ – outpouchings of intestinal wall • Colitis – inflammation of large intestine • ____ feet long • Waste stays _____ hours • Main function is ________ absorption in order to eliminate feces Appendix and Peritoneum • Vermiform Appendix – function not fully known; but thought to provide safe place for good ___________ – appendicitis • inflammation of appendix • not common in elderly • appendectomy – surgical removal of appendix • Peritoneum – large, continuous sheet of serous membrane – parietal and visceral portions – ______________ : extension of parietal peritoneum that anchors GI tract to abdominal wall. Liver • Anatomical units – lobes and lobules – – left lobe right lobe – biggest section of liver – hepatic lobules – branch of hepatic vein extends through each _______ (main • • • Blood flows to hepatic lobules via branches of the hepatic artery and hepatic portal vein ____________ _______ ________ – merger of the hepatic duct and cystic duct _________________ bile – – • Bile salts – aid in the absorption of ___________; most essential part of bile No enzymes Functions of liver – – _________________ Bile ____________________ • secrete 1 pint/day – Metabolizes proteins, fats, and carbohydrates • anat unit) Misc. Info – Hepatic refers to liver – Largest _______ in the body – Hepatitis – inflammation of the liver – ___________ – degenerative liver condition – Removes harmful substances from the blood – Stores vitamins and sugars until your body needs them • Gallbladder – ____________ bile (holds 30-50 ml bile) – Cholecystokinin (CCK) – hormone that stimulates gallbladder to release ________ into duodenum (small intestine) – Secretin – stimulates release of bile – Cholelithiasis - gallstones – Cholecystectomy – surgical removal of gallbladder – Below liver – Pear shaped Cholelithiasis - Gallbladder with yellow cholesterol gallstones Cholecystectomy Gallbladder before removal • Pancreas – Both endocrine and exocrine gland – Pancreatic juice secreted by exocrine acinar cells – Pancreatic cancer – form of adenocarcinoma – Breaks down sugar – Beta cells secrete _____________ Types of Digestion • Mechanical • Chemical Digestive Physiology Mechanical Digestion --Mastication --Deglutition --Peristalsis Oral stage – mouth to oropharynx - ___________________ control - bolus formed - soft palate acts as valve to prevent food from enetering nasopharynx Pharyngeal stage – oropharynx to esophagus - _______________________ control - epiglottis prevents bolus from entering larynx to trachea Esophageal stage – esophagus to stomach - ______________________ control Peristalsis •_____________ ripple of smooth muscle •ring of contraction occurs where GI wall is stretched, pushing bolus forward •stimulated by ______ – secreted by endocrine cells in presence of chyme Segmentation •_______________ movement •forward and backward movement that mechanically breaks down food and mixes it with digestive juices Organ Mouth (teeth and tongue) Pharynx Esophagus Stomach Small Intestine Ascending and Transverse Colon Descending Colon Rectum Mechanical Process Mastication Deglutition Deglutition Deglutition Peristalsis Churning Peristalsis Segmentation Peristalsis Segmentation Peristalsis Mass peristalsis Defecation Chemical Digestion Digestive ________________ a. extracellular, organic (protein) catalysts b. enzyme action 1. specificity 2. optimal pH Stomach pH 3.0 Jejunum Ileum Colon 6.0-7.0 7.5 6.8-7.3 3. catalyst 4. continually destroyed or eliminated, so constantly being made 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 Carbohydrate digestion (bread, potato, rice, pasta, fruit, vegetables) •Starch and sugar are broken down by saliva, pancreatic and small intestinal juices salivary amylase, pancreatic juices * starch small intestine enzymes maltose absorbed into blood glucose (monosac) liver (stored or used) small intestine enzymes * sugar (sucrose) glucose + fructose absorbed into blood * fiber – undigestible •_________________ cannot be broken down; eliminated in feces Lipid Digestion •_______________________ – bile breaks down fat into small droplets within the small intestine •Steatorrhea - impaired fat absorption producing large, greasy, foul-smelling stool micelle •Fat-soluble vitamins – ___________ (stored in liver and fatty tissue) •Pancreatic ____________ – main fat-digesting enzyme 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
