Physiology of Gastrointestinal Disorders

1. Physiology of Gastrointestinal Disorders Prof. Dr. Bayram Yılmaz Yeditepe University Faculty of Medicine Department of Physiology

2. Disorders of Swallowing and of the Esophagus • Paralysis of the swallowing mechanism • Damageto 5th, 9th andXthcranialnerves • Poliomyelitisorencephalitis • Myasthenia gravisorbotulism • When the swallowing mechanism is partially or totally paralyzed, 3abnormalities occur • Whichincludestactileandpositionsenses • Thermoreceptivesenses • Painsenses

3. Achalasia and Megaesophagus • Achalasia is a condition in which the lower esophageal • sphincter fails to relax during swallowing • Receptive relaxation of the gastroesophageal sphincter • Swallowedesophageal tubeand an inflatedballoon • Antispasmotic drugs (that relax smooth muscle) can also behelpful

4. Gastritis—Inflammation of the Gastric Mucosa • Gastric Barrier and Its Penetration inGastritis • Gastric ulcer • Gastric atrophy • Achlorhydria (and Hypochlorhydria) • Pernicious Anemia in Gastric Atrophy

5. Peptic Ulcer • A peptic ulcer is an excoriated area of stomach or intestinalmucosa caused principally by the digestive actionof gastric juice or upper small intestinal secretions

6. Peptic Ulcer • Basic Cause of Peptic Ulceration • The usual cause of pepticulceration isan imbalance between the rate of secretionof gastric juice and the degree of protection afforded by • (1) the gastroduodenal mucosal barrier and (2) the neutralizationof the gastric acid by duodenal juices

7. Peptic Ulcer • Two feedback control mechanisms normally neutralizes the gastric juices • Entero-gastric reflexes and secretin • A peptic ulcer can be caused in either oftwo ways: • (1) excess secretion of acid and pepsin by thegastric mucosa • (2) diminished ability of the gastroduodenalmucosal barrier to protect against the digestiveproperties of the stomach acid–pepsin secretion

8. Specific Causes of Peptic Ulcer • Helicobacter pylori breaks down the gastro-duodenal mucosal barrier • Alcohol • Smoking • Aspirin

9. Physiology of Treatment • Use of antibiotics • Administrationof acid-suppressant drugs, especially ranitidine (H2 receptors) • Gastric acid secretion is reduced by 70-80% • Surgical removal of stomach • Parasympathetic denervation to the gastric glands

10. Disorders of the Small Intestine • Abnormal digestion of food in the small intestine-pancreatic failure • Lack of pancreatic secretion frequently occurs • (1)pancreatitis • (2) when thepancreatic duct is blocked by a gallstone at the papillaof Vater • (3) after the head of the pancreas has beenremoved because of malignancy

11. Pancreatitis • Acutepancreatitis or chronic pancreatitis • Alcoholism as the primary cause of pancreatitis • Second major cause of pancreatitis: blockage of the papilla of Vater by a gallstone • Tripsin inhibitor and accumulation of trypsinogen

12. Malabsorption by the SmallIntestinal Mucosa: Sprue • Several diseases can causedecreased absorption by the mucosa; they are oftencalled“sprue“ • NontropicalSprue: idiopathic sprue, celiac disease (in children),or glutenEnteropathy • Tropical Sprue • Malabsorption in Sprue • Severenutritional deficiency (2) osteomalacia • (3) inadequate blood coagulationand(4) pernicious anemia

13. Disorders of the Large Intestine • Constipation • Megacolon • Hirschsprung’s disease • Deficiency of ganglio cells in the myenteric plexus

14. Diarrhea • Enteritis, Infectious diarrhea • Cholera & Treatment • Psychogenic Diarrhea: increased motility and excess mucus secretion

15. Inflammatory Bowel Disease (IBD) • Ulcerative colitis • Crohn's disease: also called regional enteritis, is a chronic inflammation of the intestines that is usually more pronounced in the ileum

16. Ulcerative Colitis • It is a disease in which extensive areas of the walls of the large intestinebecome inflamed and ulcerated

17. Vomiting • Any part of the upper GI tract becomes excessively irritated,overdistended, or even overexcitable • The sensory signals that initiate vomiting originatemainly from the pharynx, esophagus, stomach, andupper portions of the small intestines • Vomiting center in the brain stem • Motor impulses are transmitted by 5th, 7th,9th, 10th, and 12th cranial nerves to the upper GI tract

18. Vomiting • Antiperistalsis, the prelude to vomiting • Vomiting Act: • (1) a deep breath, (2) raising of the hyoidbone and larynx to pull the upper esophageal sphincteropen, (3) closing of the glottis to prevent vomitus flowinto the lungs, and (4) lifting of the soft palate to closethe posterior nares • Contraction of abdominal muscles, increased intragastric pressure, relaxation of LES and vomiting

19. Chemoreceptor Trigger Zone • “Chemoreceptor Trigger Zone” in the Brain Medulla for Initiationof Vomiting by Drugs or by Motion Sickness • It is a small area located bilaterally on thefloor of the fourth ventricle • Motion sickness

20. The motion stimulates receptors in the vestibularlabyrinth of the inner ear, and from here impulses aretransmitted mainly by way of the brain stem vestibularnuclei into thecerebellum, then to the chemoreceptortrigger zone, and finally to the vomiting center to causevomiting.

21. Nausea • Nauseais the conscious recognition of subconscious excitationin an area of the medulla closely associated with or partof the vomiting center • (1) irritativeimpulses coming from the gastrointestinal tract,(2) impulses that originate in the lower brain associatedwith motion sickness • (3) impulses from the cerebral • cortex to initiate vomiting

22. Gastrointestinal Obstruction • Some common causes of obstruction are • (1)cancer, (2) fibrotic constriction resulting from ulcerationor from peritoneal adhesions, (3) spasm of a segment ofthe gut and (4) paralysis of a segment of the gut