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Gastrointestinal System Module 1

GI System--Structure. MouthEsophagusStomachSmall IntestineLarge intestineRectumAnus. GI System--Structure. GI tract is about 30 feet long from mouth to anusLayers from inner to outerMucosaSubmucosaMuscle- 2 layersCircular (inner)Longitudinal (Outer)Serosa except esophagus (fibrous). GI System--Structure.

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Gastrointestinal System Module 1

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    1. Gastrointestinal System Module 1

    3. GI System--Structure GI tract is about 30 feet long from mouth to anus Layers from inner to outer Mucosa Submucosa Muscle- 2 layers Circular (inner) Longitudinal (Outer) Serosa except esophagus (fibrous)

    4. GI System--Structure Innervation Sympathetic-inhibitory Parasympathetic-excitatory Example: Peristalsis is increased with parasympathetic stimulation

    5. GI System--Structure GI tract receives 25-30% of cardiac output Venous blood empties into portal vein which peruses liver Upper portion of GI tract receives blood from splanchic artery Small intestine receives blood from hepatic and mesentery arteries Large intestine receives blood supply from superior and inferior mesenteric arteries

    6. GI System--Structure Two types of movement Mixing (Segmentation) Propulsion (Peristalsis) Hormones and enzymes for digestion Mucous provides protection, lubrication, water, electrolytes

    7. GI System--Structure Abdominal organs are covered by peritoneum Two layers of peritoneum Parietal-lines abdominal cavity wall Visceral-covers abdominal organs Peritoneal cavity- space between parietal and visceral Two folds of peritoneum Mesentery-attaches small intestine to posterior abdominal wall Lesser omentum-hangs from stomach like apron, contains fat and lymph nodes

    8. GI System—Intrinsic/Enteric layer GI tract has its own nervous system Enteric or intrinsic Two intrinsic layers Lies between mucosa and the circular muscle layer Other layer lies between circular and longitudinal layer Innervation contributes to coordination of GI motor and secretory activities Enteric nervous system is also known as the “gut brain” Ability to control movement and secretion of GI tract

    9. GI System-Function Supply nutrients to body cells Ingestion (taking in) and propulsion (movement) Digestion-breakdown Absorption—transfer of food products into circulation Elimination-Excreting waste products

    10. GI System-Function/Ingestion Swallowing (deglutition)-mechanical component of ingestion Mouth Lips Oral cavity Three pairs of salivary glands Parotid Submaxillary Sublingual Glands produce saliva (water, protein, mucin, salts, amylase(pytalin))

    11. GI System-Function/Ingestion Pharynx Esophagus Upper third – striated muscle Distal two thirds-smooth muscle With swallowing, peristaltic wave moves bolus into esophagus Lower esophageal sphincter (LES) remains contracted except when swallowing, vomiting, or belching LES-important barrier that prevents acid reflux from stomach

    12. GI System-Digestion/Absorption Digestion is mechanical and chemical Mouth Lubricates and softens mass Stomach Stores food Mixes food with gastric secretions Empties contents into small intestine

    13. GI System-Digestion/Absorption-Stomach Parts of stomach Fundus Chief cells (secrete pesinogen) Parietal cells (secrete HCL, water, and intrinsic factor) Acid Ph protects against ingested organisms Intrinsic factor promotes cyclocobalamin (B 12) absorption in the small intestine Body Antrum

    14. GI System-Digestion/Absorption-Stomach Pylorus Small portion of antrum Lies proximal to pyloric sphincter Pyloric sphincter guards entrance to and from entrance to stomach Rugae-folds in stomach, contains glands

    15. GI System-Digestion/Absorption-Small Intestine Two functions Digestion Absorption-uptake of nutrients from gut to bloodstream Approximately 23 feet long Extends from pylorus to ileo cecal valve (prevents reflux from small intestine to large intestine) Large surface area for absorption

    16. GI System-Digestion/Absorption-Small Intestine Villi Functional units of small intestine Contains goblet cells Secrete mucous Epithelial cells Produce digestive enzymes Mirovilli-assist villi to increase surface area Crypts of Liberkuhn-contain base columnar cells Brunner’s glands-secrete mucous in duodenum

    17. GI System-Physiology of Digestion Salivary gland-breakdown of starch Stomach-releases of pepsinogen from chief cells Acid in stomach converts of pepsinogen in to pepsin-initial breakdown of proteins Stomach has minimal impact on breakdown of starches and fat Food stays in stomach 3-4 hours

    18. GI System-Physiology of Digestion-Small Intestine Carbohydrates broken down into monosaccharides Fats to glycerol Proteins to amino acids Chyme (food mixed with gastric secretions)

    19. GI System-Physiology of Digestion-Small Intestine Enzymes secreted from pancreas Bile from liver Intestinal secretions Hormones secretin stimulates pancreas to produce bicarb (neutralizes acid in chyme) Duodenum secretes mucous to protect small intestine from acid Hormone cholecystokinin stimulates gall bladder contraction and relaxation of the sphincter of Oddi-bile released-digest fat

    20. GI System-Physiology of Elimination-Large Intestine 5-6 feet long Four parts Cecum and Appendix Colon Rectum Anus Most important function-absorption of water and electrolytes

    21. GI System-Physiology of Elimination-Large Intestine Forms feces until defecation Feces Water Bacteria Unabsorbed minerals Undigested food Bile pigment Epithelial cells

    22. GI System-Physiology of Elimination-Large Intestine Bacteria- Responsible for breakdown of proteins not digested by small intestine Synthesize Vitamin K and some B vitamins Production of flatus Slow movement-haustral churning Defecation Voluntary and involuntary muscles Valsalva maneuver

    23. Physiology of Elimination-Liver Largest internal organ in body Right and left lobes Lobules-functional unit Rows of hepatic cells (hepatocytes) Kupfer cells-phagocytic activity-removes toxins/bacteria from blood Portal circulatory system brings blood to liver from stomach, intestine Involved in metabolism, detoxification, destruction of RBC

    24. Physiology of Elimination-Biliary Tract Consists of Gallbladder-concentrate, store bile Duct system Bile-produced by hepatic cells Moves down common bile duct, enters duodenum at ampulla of Vater In intestine, bilirubin converts to stercobilirubin (color of stool) and urobilirubin (color of urine) Sphincter of Oddi keeps ampulla closed

    25. Physiology of Elimination-Biliary Tract Bilirubin metabolism Breakdown of Hemoglobin Bound to albumin for transport to liver (uncongugated) In liver, conjugated with glucuronic acid Conjugated bilirubin is soluable

    26. Physiology of Elimination-Pancreas Exocrine and endocrine functions Exocrine-digestion-pancreatic enzymes Endocrine Islets of Langerhans Beta cells-insulin Alpha cells-glucagon Delta-somatostatin F cells-pancreatic polypeptides

    27. GI System and Aging Periodontal disease-loss of teeth Taste buds, smell, salivary secretions decrease Delayed gastric emptying Motility of GI tract diminishes Decrease in HCL secretion Reduction in secretion of acid and intrinsic factor Liver size decreases

    28. GI System-Factors that Influence Function Stress/anxiety Dietary intake Ingestion of ETOH/caffeine Cigarette smoking Fatigue Organic diseases Others?

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