Digestion - The Human Digestive System The Human Digestive...

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Unformatted text preview: The Human Digestive System The Human Digestive System Health Review Dr. Adam J. Decker Georgia Institute of Technology HPS 1040 Functions of the Digestive System Functions of the Digestive System Ingest food Break down food into nutrient molecules Absorb molecules into the bloodstream Rid the body of indigestible remains Main Divisions of the Digestive Main Divisions of the Digestive System Alimentary Canal Continuous, muscular digestive tube winding throughout the body Digests and absorbs food particles Contains the following organs: Mouth, Pharynx, Esophagus, Stomach, Small and Large Intestines Accessory Digestive Organs Contains the following organs: Teeth, Tongue, Gallbladder, Salivary Glands, Liver, and Pancreas Digestive System Divisions Digestive System Divisions Digestive Processes Digestive Processes Ingestion Propulsion Mechanical digestion Chemical digestion Absorption Defecation Histology of the GI Tract Histology of the GI Tract Anatomy of the Mouth Anatomy of the Mouth Anatomy of the Tongue Anatomy of the Tongue Features and Functions of the Features and Functions of the Salivary Glands Main functions: Produces and secretes saliva Cleanses the mouth Dissolves food chemicals so they can be tasted Moistens food, compacting it into a bolus Begins the chemical breakdown of food Salivary amylase: starch Anatomy of the Salivary Glands Anatomy of the Salivary Glands Composition of Saliva: 97­99.5% water pH 6.75­7.0 Sodium, potassium, chloride, phosphate, and bicarbonate Mucin Salivary amylase Features and Functions of the Features and Functions of the Esophagus Muscular tube that propels food to stomach; bolus enters stomach through esophageal hiatus Skeletal muscle (upper third for swallowing) and smooth muscle (lower third) for peristalsis Esophageal glands – produce mucus to lubricate bolus Esophageal sphincter – prevents backflow into oral cavity Cardiac sphincter­ prevents backflow into esophagus Anatomy of the Esophagus Anatomy of the Esophagus Microscopic Anatomy of the Microscopic Anatomy of the Esophagus Deglutition and the Pharynx Deglutition and the Pharynx Peristalsis Peristalsis Features and Functions of the Features and Functions of the Stomach Temporary storage area for food and allows it to mix with gastric juice to produce chyme Regions: cardiac, fundus, body, and pyloric Greater and Lesser Curvatures: connected to greater and lesser omentums Rugae folds: longitudinal folds in stomach wall ­ mucous b/w folds Muscle layers arranged circularly, longitudinally, AND obliquely (aids in digestion) Anatomy of the Stomach Anatomy of the Stomach Microscopic Anatomy of the Microscopic Anatomy of the Stomach Simple columnar epithelium – contains gastric pits that secrete gastric juices Goblet cells – secrete mucus that coats stomach and prevents it from being digested itself Parietal cells – secrete hydrochloric acid (converts pepsinogen into pepsin) and intrinsic factor (necessary for absorption of vitamin B12) Chief cells – secrete pepsinogen which is converted to pepsin to aid in protein digestion Enteroendocrine cells – release hormones such as: Histamine, Serotonin, Gastrin, Endorphins, and Somatostatin Microscopic Anatomy of the Microscopic Anatomy of the Digestive System Gastric Motility and Emptying Gastric Motility and Emptying Peristaltic waves approach stomach and become stronger near pyloric region Pyloric sphincter allows ~ 3 mL of chyme to pass to duodenum and the rest to return to stomach for further mixing Features and Functions of the Features and Functions of the Small Intestine Receives chyme from stomach; performs majority of digestion and absorption of nutrients Regions: Duodenum (upper region receiving chyme from stomach and digestive enzymes from pancreas and bile from liver and gallbladder) Jejunum/Ileum (lower regions where absorption occurs) Plicae circulares (permanent folds in mucosa and submucosa that slow movement of chyme) Anatomy of the Small Intestine Anatomy of the Small Intestine Microscopic Anatomy of Small Microscopic Anatomy of Small Intestine Villi: fingerlike projections that increase the surface area of the small intestine. Increased surface area will enable more nutrient to tissue contact for maximum absorption. Microvilli: tiny projections on the plasma membranes of columnar cells that appear fuzzy (i.e. brush border cells). Produce enzymes that further break down nutrients: Lactase breaks down lactose Sucrase breaks down sucrose Aminopeptidase breaks down proteins into amino acids. Microscopic Anatomy of the Small Microscopic Anatomy of the Small Intestine Secretions of the Small Intestine Secretions of the Small Intestine Secretin: released by enteroendocrine cells when acidic chyme enters SI; causes release of bicarbonate­rich pancreatic juices Somatostatin: slows gastric motility and emptying and inhibits production of gastric secretions Cholecystokinin (CCK): released when fatty, protein­ rich chyme enters SI; causes release of enzyme­rich pancreatic juices and bile Brush border enzymes: process long peptides, nucleic acids, and sugars into smaller ones After Digestion: Absorption After Digestion: Absorption Protein Fats Functions of the Liver Functions of the Largest internal organ Functions: Filters and processes nutrient­rich blood of carbohydrates, proteins, and lipids from intestine Production and regulation of cholesterol Production of bile which emulsifies fats Removes drugs and hormones from circulation Storage of vitamins and minerals Gross Anatomy of the Liver Gross Anatomy of the Liver Regulation of Bile Production Regulation of Bile Production Bile exits cystic duct upon stimulation CCK released when acidic, fatty chyme enters intestines Causes: Gallbladder Contraction Pancreatic Juice Secretion Relaxation of hepatopancreatic sphincter Features and Functions of the Features and Functions of the Large Intestine Functions: Reabsorption of remaining water and electrolytes Production and absorption of Vitamins B and K Elimination of feces Diameter is only 7 cm but is larger than that of the small intestine Gross Anatomy of the Large Gross Anatomy of the Large Intestine Teniae Coli: bands of smooth muscle that create pocket­like sacs (haustra) Cecum: sac­like connection between the small and large intestines Appendix: small structure containing lymphoid tissue; small immune function Ascending, Descending, Transverse, and Sigmoid Colon Splenic and hepatic flexure Rectum: storage area Anus: regulates defecation with two sphincter muscles; internal and external Anatomy of the Colon Anatomy of the Colon Summary of Digestion Summary of Digestion Summary of Digestion Summary of Digestion The Process of Absorption The Process of Absorption Clinical corner Clinical corner Peptic ulcers ­ gastric and duodenal, caused by Helicobacter pylori, NSAIDS, HCl hypersecretion Cirrhosis ­ scarred liver due to chronic inflammation Hepatitis – liver inflammation: viral, cancer, alcohol. Biliary calculi ­ gall stones ­ crystals of cholesterol in bile Borborygmus ­ rumbling noise caused by Cholecystitis ­ inflammation of gall bladder Colitis ­ inflammation of colon Dysphagia ­ difficulty in swallowing Enteritis ­ inflammation of the intestines Flatulance/erucation ...
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This note was uploaded on 02/14/2012 for the course HPS 1040 taught by Professor Surrency during the Spring '08 term at Georgia Tech.

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