Human Anatomy, 3rd edition Prentice Hall, © 2001 Gastro-intestinal tract

Human Anatomy, 3rd edition Prentice Hall, © 2001 Introduction Structure of the digestive system –A tube that extends from mouth to anus –Accessory organs are attached Functions include –Ingestion –Movement –Digestion –Absorption –Defecation

Human Anatomy, 3rd edition Prentice Hall, © 2001 Overview of Digestive System

Human Anatomy, 3rd edition Prentice Hall, © 2001 Histological Organization Same basic arrangement of tissues from esophagus to anal canal Four layers (from innermost to outermost) –Mucosa –Submucosa –Muscularis –Serosa

Human Anatomy, 3rd edition Prentice Hall, © 2001 Movement and Mixing of Digestive Materials Peristalsis –Coordinated motion of two muscular layers –Circular muscles contract, then longitudinal muscles Segmentation –Mixing of food –Circular muscles in two areas contract –Longitudinal muscles alternately contract & relax

Human Anatomy, 3rd edition Prentice Hall, © 2001 External Anatomy of the Stomach

Human Anatomy, 3rd edition Prentice Hall, © 2001 The Stomach Same 4 basic layers When the stomach is empty, the mucosa lies in large folds –Rugae Pyloric sphincter separates stomach from small intestine

Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Stomach Mucosa is simple columnar epithelium with goblet cells Mucosa is folded to form gastric pits –Gastric glands secrete gastric juice

Human Anatomy, 3rd edition Prentice Hall, © 2001 Gastric Gland Several kinds of cells produce substances that form gastric juice –Mucus cells –Chief cells –Parietal cells –Enteroendocrine cells

Human Anatomy, 3rd edition Prentice Hall, © 2001 Functions of the Stomach Mechanical digestion –Food reaches pylorus Chemical digestion –Digestion of proteins Absorption –No food –Water, electrolytes –Some drugs –Alcohol

Human Anatomy, 3rd edition Prentice Hall, © 2001 The Small Intestine About 18 feet long The duodenum –About 8 inches long –Common bile duct & pancreatic duct empty here The jejunum –About 8 feet long –Most digestion occurs here The ileum –About 9.5 feet long –Most absorption occurs here –Ends in the ileocecal valve

Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Small Intestine The lining is folded into circular pleats –Plicae circulares The mucosal surface is folded into villi The epithelial cell membranes are highly folded into microvilli Intestinal glands are found in the crypts at the base of villi –Secrete intestinal juice

Human Anatomy, 3rd edition Prentice Hall, © 2001 A Villus

Human Anatomy, 3rd edition Prentice Hall, © 2001 Functions of the Small Intestine Chyme is further broken down –Proteins –Carbohydrates –Fats Most absorption is in the small intestine

Human Anatomy, 3rd edition Prentice Hall, © 2001 The Large Intestine (Colon) About 4.5 feet long Mesocolon supports Begins with the cecum Appendix is attached Ascending colon Transverse colon Descending colon Sigmoid colon Colon connects to rectum Rectum connects to anal canal Empties to the exterior through the anus

Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology and Functions of the Large Intestine Mucosa - simple columnar epithelium –Completion of absorption –Formation of feces Lots of mucus glands Expulsion of feces from the body

Human Anatomy, 3rd edition Prentice Hall, © 2001 Digestion in the Large Intestine Mechanical –Regulated by the ileocecal valve –Mixing and peristalsis –Mass peristalsis Chemical –Mucus secreted –No enzymes –Bacteria – prepare chyme for elimination

Human Anatomy, 3rd edition Prentice Hall, © 2001 Feces Formation & Defecation Chyme is now solid or semi-solid - feces Large intestine absorbs any more water and electrolytes from feces Defecation –Mass peristalsis pushes fecal material into rectum –Rectum stretches Defecation reflex

Human Anatomy, 3rd edition Prentice Hall, © 2001 Accessory Organs Liver Pancreas Gall bladder

Human Anatomy, 3rd edition Prentice Hall, © 2001 The Liver Performs many life- sustaining functions Location – under the diaphragm on the right –Connected to the diaphragm by the falciform ligament Divided into lobes –Right lobe –Left lobe –Caudate lobe –Quadrate lobe

Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Liver Outside is a capsule Composed of tiny lobules Each lobule is surrounded by liver cells and sinusoids –Hepatocytes –Kupffer cells Bile ducts run between liver cells

Human Anatomy, 3rd edition Prentice Hall, © 2001 Functions of the Liver Produces bile – the primary digestive function –Composition Water Bile salts Cholesterol Pigments –Bilirubin –Digestive function Emulsification of fats

Human Anatomy, 3rd edition Prentice Hall, © 2001 Other Functions of the Liver Absorbs and stores iron, vitamins A, D, E, B7, K Detoxifies toxins and hormones Metabolizes proteins, carbohydrates, and lipids Removes bacteria from the blood Produces plasma proteins Removes worn-out and damaged red blood cells

Human Anatomy, 3rd edition Prentice Hall, © 2001 The Gallbladder Location – underside of right lobe of liver Function – concentrate and store bile –Collected from liver Hepatic ducts –Adds bile to duodenum Cystic duct Common bile duct Gallstones

Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pancreas Location – in the curvature of the duodenum Connected to the duodenum by the pancreatic duct Produces pancreatic juice Functions –Exocrine - digestion of all nutrient groups –Endocrine – control blood glucose level

COMMON LABORATORY PROCEDURES Lower GIT study: barium enema Examines the lower GI tract Pre-test: Clear liquid diet and laxatives, NPO post-midnight, cleansing enema prior to the test

COMMON LABORATORY PROCEDURES Lower GIT study: barium enema Post-test: Laxative is ordered, increase patient fluid intake, instruct that stools will turn white, monitor for obstruction

COMMON LABORATORY PROCEDURES EGD esophagogastroduodenoscopy Intra-test: position : LEFT lateral to facilitate salivary drainage and easy access

APPENDICITIS Obstruction Fecalith, Kinked appendix, inflammation, neoplasm Inflammatory response Increased Intraluminal Pressure WBC Infiltration Pus formation Necrosis Perforation Edema Peritonitis