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PP Slides Chap 38 GI Physiology (1).ppt
PP Slides Chap 38 GI Physiology (1).ppt
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Advanced Pathophysiology Structure and Function of the Digestive System Chapter 38 Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. Gastrointestinal Tract Mouth Esophagus- 25 cm long Upper and lower esophageal sphinctors Stomach Small intestine Large intestine Rectum Anus * Gastro- intestinal Tract * Gastrointestinal Tract Functions: Overview Breaks down ingested food Prepares food for uptake by the body?s cells Provides body water Eliminates wastes Controlled by hormones and the autonomic nervous system (except for chewing, swallowing, and defecation) * Gastrointestinal Tract Ingestion of food Propulsion of food and wastes from the mouth to the anus Secretion of mucus, water, and enzymes Mechanical digestion of food particles Chemical digestion of food particles Absorption of digested food Elimination of waste by defecation * Gastrointestinal Tract Histology Mucosa Submucosa Muscularis Serosa or adventitia Enteric plexus Submucosal plexus Myenteric plexus Subserosal plexus * Gastrointestinal Tract * Mouth Reservoir for chewing and mixing of food with saliva Taste buds Salty, sour, bitter, and sweet Olfactory nerves Teeth 32 permanent teeth * Salivary Glands Three pairs Submandibular Sublingual Parotid Saliva Water with mucus, sodium, bicarbonate, chloride, potassium, and salivary ?-amylase (carbohydrate digestion) Breaks down starch to maltose Controlled by sympathetic and parasympathetic fibers * Swallowing Complex event mediated by the swallowing center, located in the reticular formation of the brainstem; also involves other brain regions, including the insula/claustrum and cerebellum The swallowing center and respiratory center provide the coordinating innervation Superior constrictor muscle of the pharynx contracts, prevents movement of food into the nasopharynx Respiration inhibited and epiglottis slides downward to prevent bolus from entering larynx and trachea Movements of tongue and pharyngeal constrictors propel the food into the esophagus in a series of coordinated events taking 1 or 2 seconds * Swallowing Esophagus Esophageal Peristalsis Primary( just after oropharyngeal phase) and secondary peristalsis Upper esophageal sphincter Lower esophageal sphincter Phases Oral and pharyngeal phases Esophageal phase * Stomach A hollow, muscular organ that stores food, secretes digestive juices, mixes food with the juices, and propels partially digested food (chyme) Muscle layers 3 layers unlike the rest of the GI tract) Longitudinal Circular Oblique * Stomach Boundaries Cardiac orifice (top of stomach) At the lower esophageal sphincter (LES) Pyloric sphincter Food then passes into the pylorus into duodenum Pylorus Functional areas Fundus- esophagus enters Body- w/ greater and less curvatures Antrum- w/pylorus * Stomach * Gastric Motility Swallowing- causes fundus to relax Hormones that ? gastric contractions Gastrin; Cholecystokinin; Motilin Vagus N. (parasympathetic stimulation) Hormones that ? gastric contractions Secretin Sympathetic N stimulation Gastric emptying Depends on volume and type of foot * Gastric Secretion The stomach secretes large volumes of gastric juices Normally the empty stomach has 50 cc of fluid) Mucus Acid- Dissolves food; bacteriocidal and converts pepsinogen to pepsin Enzymes Hormones Intrinsic factor Gastroferrin * Gastric Secretion Gastric pits- in to mucosa (inner-most layer) Contains a euct for several glands Gastric glands Parietal cells Hydrochloric acid and intrinsic factor IF is a mucoproteins required for absorptiion of Vit B12 Chief cells Pepsinogen G cells Gastrin * Gastric glands Enterochromaffin-like cells Histamine D cells Somatostatin Somatostatin (also known as growth hormone-inhibiting hormone (GHIH) or somatotropin release-inhibiting factor (SRIF) a peptide hormone that regulates the endocrine system somatostatin acts on the acid-producing parietal cells decreases stomach acid production by preventing the release of other hormones, including gastrin, secretin and histamine. * Gastric Pits and Gastric Glands * Gastric Secretion Phases of gastric secretion Cephalic phase See, smell, taste, chew Vagus nerce (parasympathetic) insulin Gastric phase Stim by stomach distension Intestinal phase Movement of chyme into duodenum ? gastric secretion and motility. * Small Intestine 5 to 6 meters long Three segments Duodenum- begin at pylorus and end at jejunum at Treitz ligament Jejunum Ileum Ileocecal valve- sphinctor which controls flow of food into L Intestine Peritoneum a double layer membrane that covers the organs and lines abdominal cavity. Peritoneal cavity Space between the visceral and parietal layers of the peritoneum. * Small Intestine Muscle layers Outer?longitudinal Inner?circular Mucosal folds (plica)- slow the passage of food Villi ? functional units for absorption Microvilli- on surface of columnar epithealium Brush border created by microvilli ? surface area for absorption Lamina propria- Cnt layer just under the columnar epithelium Lacteal- a lymphatic channel w/in each villus for the absorption of fat * Small Intestine * Intestinal Digestion and Absorption Carbohydrates? ribose Salivary and pancreatic amylase Proteins ? small peptides (3-6 AA) will be absorbed Pepsin-HCl, trypsin, chymotrypsin, Fats ? FA and glycerol Lipase, phospholipase and cholesterol esterase Water- will not pass intact membranes-do passes through tight junctions and intercellular spaces Electrolytes- Na-+ is exchanged for H+ and Cl- is exchanged for HCO3- * Intestinal Digestion and Absorption * Intestinal Digestion and Absorption * Large Intestine 1.5 M long Cecum- begins at the ileocecal valve Appendix Colon- 4 parts: Ascending Transverse Descending Sigmoid Rectum Anus * Large Intestine * Large Intestine Ileocecal valve O?Beirne sphincter- controls movement of waste from sigmoid to the rectum Internal anal sphincter External anal sphincter Taenia coli- 3 longitudinal bands in the longitudinal M. Haustra Circular outpounching in the circular M. * Gastrointestinal Absorption * Intestinal Bacteria Stomach environment is relatively sterile because of secreted stomach acid Bile acid secretion, motility, and antibody production keep bacterial numbers in the duodenum to a minimum A low concentration of aerobes in the jejunum Anaerobic bacteria distal to the ileocecal valve Anaerobes are 95% of the fecal flora in the colon * Accessory Organs of Digestion * Accessory Organs of Digestion Liver- largest solid organ in body Lobes- in RUQ has two lobes: Separates lobes and attached to the anterior abdominal wall by the falciform ligament Right lobe- larger, right lateral lobe Left lobe Blood suppply to Liver via Hepatic A. (Br. Of Abdom aorta) Hepatic Portal V. supplies blood to liver with nutrients from the digestive tract. * Liver * Hepatic Portal Circulation * Liver Liver lobules within the 2 lobes Hepatocytes Lipocytes- store fat and Vit A Sinusoids Bile canaliculi Common bile duct Major duodenal papilla (sphincter of Oddi) * Liver Lobules Kupffer cells- phagocytic cells that line the liver sinuses * Secretion of Bile Alkaline, bitter-tasting, yellowish-green fluid that contains bile salts, cholesterol, bilirubin( a pigment), electrolytes, and water Formed by hepatocytes and secreted into the bile canaliculi Eventually drain into the common bile duct Enterohepatic circulation Recycling of bile salts (bile acids for then intestinal emulsification and absorption of fat) * Entero- hepatic Circulation * Metabolism of Bilirubin Aged RBC are phagocytized by macrophages in the liver (Kupffer cells) and spleen and produces Bilirubin. Broken down into heme and globin Heme is broken down, iron removed to create biliverdin and then bilirubin. Gives bile a greenish black color and produces the yellow tinge of jaundice Unconjugated bilirubin- free, in plasma Conjugated bilirubin- in liver, combined with glucuronic acid- when released in to the colon becomes deconjugated and called Urobilinogen (fund in the urine and stool) * Metabolism of Bilirubin * Vascular and Hematologic Liver Functions Blood storage Bacterial and foreign particle removal Synthesizes clotting factors Plasma proteins, complement Produces bile to absorb fat-soluble vitamins (A, D, K, E) Metabolizes fats * Vascular and Hematologic Liver Functions Metabolizes proteins Metabolizes carbohydrates Metabolic detoxification Storage of minerals and vitamins * Gallbladder A sac-like organ that lies on the inferior surface of the liver Function is to store and concentrate bile between meals Gallbladder Bile flows from the liver to the duodenum via hepatic duct or to GB via cystic duct. From GB to common Bile duct. holds about 90 ml of bile * Exocrine Pancreas Composed of acini and networks of ducts that secrete enzymes and alkaline fluids to assist in digestion Pancreatic duct Ampulla of Vater * Exocrine Pancreas * Exocrine Pancreas 20 cm long- fits into the ?c-shaped? duodenum, post to stomach Secretions via pancreatic duct Potassium, sodium, bicarbonate, magnesium, calcium, and chloride Enzymes Trypsinogen, chymotrypsinogen, and procarboxypeptidase Trypsin inhibitor Pancreatic ?-amylase Pancreatic lipase * Aging and the Digestive Function Tooth enamel and dentin wear down Teeth are lost Periodontal disease Gum recession Osteoporotic bone changes * Aging and the Digestive Function Number of taste buds decline Sense of smell diminishes Salivary secretion decreases Decreased esophageal and gastric motility * Diagnostic Tests to Evaluate GI Function Stool Culture Occult blood X-rays Plain; Barium upper and lower GI IV/Oral cholecystogram Abdom US cholecystnography (US for gall stones) Ct and MRI Endoscopy Breath tests lactose intolerance helicobacter * LFTs- liver enzymes and others ALT (SGPT)- Serum alanine aminotransferase S Previously called serum glutamate pyruvate transaminase ? w/ liver injury or necrosis AST (SGOT) Serum aspartate aminotransferase Previously Serum glutamic oxaloacetate trassferase SGGT- Serum gamma glutamyl transpeptidease Alkaline Phosphatase Serum Bilirubin Albumen Prothrombin time(PT) *
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